A substantial change of paradigm in audiovisual preservation began as early as 25 years ago. Until then, audio and video preservation followed the traditional pattern that is still valid for archives of text documents and museums around the world: To safeguard the objects placed in their care.

Around 1990, however, audio archivists began to realise that following this principle would ultimately be in vain. It was becoming obvious — and this is the topic of this publication — that audio and video carriers are vulnerable. Most are unstable when compared with the great majority of text documents. Moreover, being machine-readable documents, the availability of replay equipment was equally important for the retrieval of their contents as carrier integrity.

By that time, it was also becoming obvious that the digital technologies and the enormous pace of technical innovation was creating new formats in an ever faster sequence and, therefore, with ever shorter life cycles. This would confront archivists with the additional challenge of keeping the format specific replay equipment for an ever-growing number of formats in operable condition.

This led to the change of paradigm: Safeguard the content, not the original carrier, was the new mantra. This is achieved by copying the contents from one preservation platform to the next. In order to avoid copying losses, copying has to be done in the digital domain. Analogue contents have, therefore, to be digitised and, together with pre-IT digital contents, converted into files. These will be safeguarded like all other computer files by adequately equipped and managed digital repositories.

While in its beginnings this new paradigm was not accepted without dispute, it was widely adopted for audio archiving from the early 1990s onward and was accepted soon after by video archivists. Meanwhile, because of the global change from analogue to digital film projection and the retreat of the industry from the production of analogue film, this principle is now also widely applied in film preservation.

IASA members have been active players in this process, and IASA as an organisation has always provided an open platform for this development. As a consequence, this principle has been codified as a standard by the IASA Technical Committee in The Safeguarding of the Audio Heritage: Ethics, Principles and Preservation Strategy, colloquially referred to as IASA-TC 03. This is now in its third version and available in eight languages. The message, in a nutshell, is:

Long-term preservation of audio (and implicitly also for video) can only be achieved by converting contents into files, and by maintaining these files like any other computer data.

Consequently, after codification of the principle, in 2004 IASA published IASA-TC 04, Production and Preservation of Digital Audio Objects, and is preparing IASA-TC 06, Production and Preservation of Digital Video Objects.

More information about these publications can be found on the IASA website at http://www.iasa-web.org/iasa-publications.

Why does IASA now publish this document at the end of the era of traditional audiovisual carriers?

It is true that a considerable part of the worldwide audio and video holdings¹—typically those owned by broadcasting and national archives of wealthy countries—have already been digitised, or are on their way to being digitised for long-term preservation. Although the new methodology of audiovisual long-term preservation had been universally accepted by the end of the 20th century, there remains a considerable part of the audiovisual legacy that is still stored on its original carriers. The main reason is obviously the lack of funds. But also lacking is a sense of urgency to complete the digitisation of content.

There is an ever-decreasing time window to complete the digitisation process before the small pool of equipment in operable condition required for the replay of traditional formats vanishes. Today, this window is estimated to be between 10 to 15 years², which makes the provision of optimal storage conditions imperative. This is particularly important for archives in hot and humid climatic zones. The purpose of this publication is to assist stakeholders to optimise storage conditions as an interim measure before professional longterm preservation through digitisation can be funded and organised.

Additionally, optimisation of life expectancy assists the archive to follow the recommendations of IASA-TC 03 to keep the originals in good storage after digitisation as a safeguard against technical advances making better copies possible.

Under no circumstances, however, must these guidelines be misunderstood as being a complete solution. It is dangerous to assume that conventional conservation (passive preservation) may be a viable method for achieving the long-term preservation of, for example, a mixed media collection. Inevitably, deterioration will progress and will ultimately limit the retrievability of stored signals. An even greater threat is the increasing difficulty of obtaining working replay equipment and spare parts to keep machines operating. For several tapebased formats, the shortage of replay equipment is already very severe. Sooner or later, even the most carefully preserved carriers will become totally unplayable. Active preservation by following IASA-TC 03 and TC 04 is absolutely imperative.

1. The world-wide archival holdings of audio and video carriers have been roughly estimated to amount to 200 million hours. This estimate, however, includes multiple copies.

2. On average, for magnetic tape based documents this time window may be even shorter, for mechanical and optical carriers probably longer.

TC 05 concentrates on measures to optimise conditions for the preservation of physical and chemical integrity of traditional, haptic audio and video carriers. It concentrates on those carriers of recording systems that have been accepted by the market, and form 99% (or more) of all audio and video collections. It is not a handbook of audiovisual recording systems. Therefore, it does not discuss the vast variety of instantaneous audio discs, or rarely used recordings systems like magnetic wire or steel tape, Philips-Miller, Selenophone, etc., and mechanical video discs such as TED. The mainstream recording systems, however, are explained to some degree, in order to provide a basic understanding of the specific function and features of carriers: why and how handling and storage could negatively or positively influence their physical and chemical integrity, and what influence damage and/or deterioration processes would have on signal retrieval.

TC 05 is not a catalogue of mere Dos and Don’ts. Optimal preservation measures are always a compromise between many, often conflicting parameters, superimposed by the individual situation of a collection in terms of climatic conditions, the available premises, personnel, and the financial situation. No meaningful advice can be given for all possible situations. TC 05 explains the principal problems and provides a basis for the archivist to take a responsible decision in accordance with a specific situation. This is the reason why, for example, climatic storage ranges are recommended rather than strict figures, which often trigger a false feeling of security, whereas each chosen value is only a compromise. This is also the reason why TC 05 does not provide a general “Code of Practice”, as this would hardly fit the diversity of structures, contents, tasks, environmental and financial circumstances of collections. However, archives are strongly encouraged to develop and codify, within the limits of physical and chemical constraints, their specific rules of procedures.³

This set of guidelines is broadly divided into two main parts. The first part (Section 2), explains the main types of audio and video carriers, their composition and recording principles, physical and chemical stability, and deterioration caused by normal replay.

The second part (Sections 3–5), advises on best practice for passive preservation through careful handling and appropriate storage and transport conditions.

It should, finally, be noted that cleaning and restoration of carriers is not part of this publication. These aspects are part of signal extraction and discussed in IASA-TC 04, chapter 5. The bibliography lists books and articles, including electronic information, which have become the “mainstream” of audiovisual preservation literature. Generally, the information and recommendations of this publication that are based on common and undisputed knowledge are not specifically referenced. However, references are given when — because of new experiences or information, or research — new recommendations are made or deviations from the mainstream of earlier recommendations are suggested. In addition, it should be noted that this book also contains primary source information: observations and appraisals based on the experiences of the authors gathered over years and decades.

As these guidelines concentrate on handling and storage, there is generally no discussion of variants and discrepancies between publications concerning composition and/ or deterioration of materials.

Cross-references to IASA-TC 04 are made to the second edition (2009) of these guidelines.

3. The British Library National Sound Archive Code of Principles may serve as a structural example. In A.Ward 1990, Appendix 1.

This is a publication within the series of the IASA Technical Committee: Standards, Recommended Practices and Strategies.

Contributing authors are the following TC members:

George Boston
Kevin Bradley
Mike Casey
Stefano Cavaglieri
ean Marc Fontaine
Lars Gaustad
Albrecht Häfner
Stig-Lennard Molneryd
Richard Ranft
Dietrich Schüller
Nadja Wallaszkovits

and the guest authors

Friedrich Engel
Patrick Feaster
Sebastian Gabler

Unless otherwise quoted: Technical drawings are by Albrecht Häfner, photographs by Dietrich Schüller and Nadja Wallaszkovits.

The publication was reviewed by the IASA Technical Committee.

This text has been composed and checked with great diligence. It represents today’s knowledge and the present foresight of risks. However, the great variety of materials, and of concrete environmental and handling factors may require individual solutions, for which this text is aimed as a general guideline. Many aspects determining the physical and chemical stability of carriers and their components are yet not fully understood. Therefore, neither the editors, the authors, the Technical Committee, nor IASA as an association may be held responsible for any damage or loss which might be ascribed to the recommendations or opinions expressed in text.

The editors would be indebted for comments on possible omissions, mistakes, or new development or experiences that may shed new light onto the recommendations given.

English language editing was in the hands of George Boston. As many readers of this document will be non-native English speakers, simplicity of expression was the aim. Like the other IASA-TC publications, orthography follows UK rules.

Cooperative publications involving experts actively engaged in their daily professional lives are a challenging task. Consequently, the completion of these guidelines took longer than originally expected. The editors would like to express their gratitude to the contributors for their input, the Technical Committee for its review and support, IASA Editors Bertram Lyons and Richard Ranft for their assistance and substantial efforts in converting the manuscript into print and web editions, and, eventually, the IASA Board, IASA members and other readers for their patience in waiting for its completion.

Dietrich Schüller
Albrecht Häfner
September 2014

Magnetic recording was invented in the 19th century. Recording devices using steel wire or steel tape were used on a small scale in parallel to cylinders and gramophones. The technology became used on a greater scale with the development of magnetic tape in its modern form in the 1930s.

Optical carriers are the oldest audiovisual carriers. They have been in use for analogue image representation for more than 170 years. For the storage of audio and video signals, however, they are amongst the youngest group of carriers. Although optical tape formats have been developed, they have not reached market acceptance. Therefore, optical audio and video carriers are restricted to disc¹³ formats.

13. Spelling of disc vs. disk; this publication joins the orthography of IASA-TC 04, second edition: all analogue and optical discs are spelled discs; magnetic disks are spelled disk.

Solid-state memories are electronic circuit storage devices without any moving parts. These have been developed since the 1950s using various technologies. Of particular interest in the context of this publication are the so-called flash cards, developed since the 1990s. As removable data carriers they come in various formats (SD and several others) and as so-called USB-sticks. With an increase in storage capacity, accompanied by a dramatic drop in price, they have become popular as removable data carriers and, more recently, as replacement for HDDs in lightweight notebooks.

2.4.1 Recording principle and stability. Flash memories belong to the group of non-volatile solid-state memories, which retain their information without power supply. The memory cells consist of transistors, which can hold their information for many years. While reading capacity is generally described to be indefinite, programming/erase cycles are quoted to be between several thousand up to one million. Because of their relative sturdiness against mechanical shock and extended temperature ranges, they were originally employed in military applications.

As to their life expectancy, no realistic guesses are available. This is of minor interest as long as prices are significantly higher than HDDs. This makes them (still) unattractive for longterm storage. Although, in general, flash memories have proved their robustness for short term storage, specifically for location recording even under adverse conditions, it is imperative not to rely on a single carrier but to copy the contents at the earliest opportunity to another storage medium before arranging transfer to a secure digital storage system.

Water is the greatest natural enemy for all audiovisual carriers. It has direct chemical and indirect influences on the stability of carriers. Direct chemical influences are hydrolysis and oxidation of several carrier components as well as dissolution of some carrier materials.

3.1.1 Hydrolysis is a chemical reaction involving water, omnipresent in form of humidity in the air, as the central agent. Some polymers are prone to hydrolysis. Acids and metal ions act as catalysts in supporting such processes. The reaction changes the chemical and the physical properties of the original polymer, often producing a by-product that acts as an auto-catalyst that enhances the destructive process. Some hydrolytic processes are (partly) reversible; others are not.

3.1.1.1 Vinegar syndrome. A widely known hydrolytic polymer breakdown is the so-called vinegar syndrome. This process that deteriorates cellulose acetate (CA) films beyond retrievability, was first observed in the late 1940s. It has, however, been more widely experienced since the 1980s, particularly in tropical film archives. Acetic acid is one of the products of the process of hydrolysis of CA and acts as an auto-catalyst to accelerate the chemical reaction. Because of its smell it has become known as vinegar syndrome. With the advancement of the process, affected films lose their structure and become unplayable.

Magnetic film sound carriers with a base of CA are particularly at risk because of the catalytic properties of metal in the form of the iron oxide used as the magnetic pigment. Cellulose acetate audio tapes are also affected, but not, however, to the same disastrous degree as films because of their sub-critical mass. Apart from smell, acid detection strips assist to objectively assess the process. CA hydrolysis is not reversible.

3.1.1.2 Pigment binder degradation. Some binders of modern magnetic tapes (2.2.1.1.2) are also prone to hydrolysis causing the tapes to become sticky. Because the symptoms of this kind of hydrolysis are reversible to some degree, such tapes can generally be reconditioned for replay by exposing them to low humidity and elevated temperatures or a combination thereof. For details see IASA-TC04, 5.4.3.3. Recent research has, however, revealed that hydrolysis of binder is only one of several reasons for the so-called sticky shed syndrome (2.2.1.1.2).

3.1.2 Direct contact with water. Direct short contact with water is only dangerous for some kinds of instantaneous discs such as those made from gelatine, cardboard etc, and for hard disk drives. For other carriers water is not immediately dangerous, as long as the contact is short, the carriers are carefully cleaned if the water was dirty, and the carriers are thoroughly dried soon after coming into contact with the water. In fact, cleaning with de-ionised water is a recommended step in preparing vinyl and shellac discs for replay using a professional disc-cleaning machine (IASA-TC 04, 5.2.3, 5.3.3).

The major problem with carriers exposed to water influx is the logistical challenge of cleaning and drying the contaminated carriers, particularly for magnetic tape cassettes. Another logistic problem is the separation of carriers from paper and carton materials, such as LP albums, and the drying of those, before they become affected by mould. If greater quantities are affected, vacuum freeze drying, successfully developed for the rescue of paper and book materials, may be the only chance to safeguard paper and carton materials accompanying audiovisual material. The applicability on audiovisual carriers themselves and specifically on magnetic tape, has, as yet, not been sufficiently investigated (for influx prevention see 4.2).

3.1.3 Oxidation is another chemical reaction triggered by water. It is a potential threat to non-oxidic, pure metal particle magnetic pigments as used for compact cassettes type IEC IV, for R-DAT and for most digital video formats (2.2.1.1.1.2). Oxidation also affects the reflective layers of optical discs, except for those made of gold.

3.1.4 Dimensional influences. Humidity has also an influence on the dimensions of materials used as components of audiovisual carriers. For CA tapes, the humidity related expansion coefficient is quoted to be 15 times higher than that for polyester based tapes.16 A considerable dimension change must also be taken into account for several materials used for instantaneous discs, such as cardboard, gelatine, or the information carrying lacquer.

3.1.5 Indirect influence through bio-degradation. Water causes bio-degradation, specifically mould (fungus growth), which happens at prolonged exposure to relative humidities (RH) of 70% and higher. Fungi of various kinds are present everywhere in the world and affect nearly all audiovisual carriers. Fungi “eat” the surface of analogue mechanical carriers, which leads to excessive surface noise—a particular problem with wax cylinders. Fungi grow on magnetic tape pigment layers, which renders replay difficult or impossible. Fungi are also known to affect CDs, rendering them unplayable. Chemical prevention of fungus must be seen as a last resort. Unfavourable chemical interactions, particularly with the variety of magnetic pigment binder formulations that exist, can never be excluded. Chemical treatment may also endanger the health of archive staff.

Because of its potential for unfavourably influencing carriers, both directly and indirectly, fungus growth must be prevented by keeping relative humidity low. Any direct contact with water, even when permissible in principle, must be kept as short as possible.

3.1.6 Humidity/temperature interrelation. It must be noted that relative humidity and temperature are interrelated (for more details see 3.2.3).

3.2.1 Physical influences.

3.2.1.1 Dimensional influences. Temperature influences the size of materials: generally, carriers expand with rising and shrink with falling temperatures. This is also true for tapes. Polyester tapes have the lowest thermal expansion coefficient, while that of CA is quoted to be three times higher.

With CA and PVC tapes, this leads to looser tape packs if temperatures rise and to tighter packs with lower temperatures. With PET base films, however, there is one anomaly: these are pre-tensilised which causes their thermal expansion coefficients to be significantly higher in the dimension of thickness than of length. Thus, wound-up PET tapes “swell” with rising temperatures — each layer of tape becomes thicker — which is not compensated by elongation. This increases the tension within the tape pack. Conversely, PET tapes become 16 FIAF 1986, 11.1.1.2. looser with falling temperatures. This calls for different relaxation measures for CA and PVC tapes to those for PET tapes when changing climatic storage conditions (3.2.4).

Dimensional changes are particularly dangerous for lacquer discs. Because of the different thermal expansion coefficients of the metal or glass substrate and the brittle lacquer coating, a temperature change may trigger the cracking of the latter.

Because of these disadvantages and potential threats, specifically for tape materials and lacquer discs, the stability of temperature is of greater importance than the chosen absolute value (see 3.3).

3.2.1.2 Irreversible influences on polymers. For some polymers used as components of audiovisual carriers, elevated temperatures have an irreversible influence. If heated beyond certain temperatures, their properties are changed and are not restored after lowering the temperature again. Temperature thresholds differ widely for various materials, but it can be stated that temperatures up to 35°C do not cause any immediate irreversible effects or lead to any deterioration of any current audiovisual carrier.

3.2.1.3 Thermoplastic materials. This group of polymers softens at higher temperatures. These polymers are used for the production of containers, cassette shells, etc. The inadvertent exposure of such materials to elevated temperature, even to sunlight, may lead to an irreversible deformation. This is also a specific threat to vinyl discs.

3.2.1.4 Print-through. Temperature influences print-through on magnetic tape: the rise of print through versus time is steeper with higher, and flatter with lower temperatures (see 3.7.2.5).

3.2.1.5 Curie point. Magnetic stability (coercivity) depends on temperature. At and beyond the Curie point, magnetic stability is lost. The lowest Curie point of widely used magnetic pigment is 128°C for CrO2, while the point for iron and iron oxide is above 300°C. This phenomenon, however, is positively employed in magneto-optical recording (2.3.1.4).

3.2.1.6 Temperature range. In order to extend life expectancy, photographic materials are often stored at temperatures below the freezing point. For magnetic tape, cold storage is discouraged because some, not all, lubricants exudate at a temperature below 8°C (2.2.1.1.1.4). At the higher end, 35°C should not be exceeded (3.2.1.2). Within this range, temperature only affects the physical dimensions of carriers and the speed of chemical processes.

3.2.2 Indirect chemical influence. Temperature determines the speed of chemical processes and, therefore, ageing or deterioration. Subject to the limits set out in 3.2.1.6, it can be stated as a rule of thumb that the speed of chemical processes is doubled by an increase of 10°C, or, on the other hand, the speed of ageing is slowed by 50% by lowering temperature by 10°C — a doubling of life expectancy.

3.2.3 Humidity and temperature interrelation. Temperature determines the absolute amount of water air can hold in gaseous form (vapour). Higher temperatures hold higher amounts of vapour, while lower temperatures hold less. If a given room is cooled without simultaneously dehumidifying the air, the relative humidity rises until 100% RH is reached. At this temperature, called the dew point, superfluous vapour condenses in the form of water on the coldest surfaces (see figure 30). Any air conditioning must, therefore, control both parameters simultaneously (see 4.3). Most conventional air conditioning equipment does not dehumidify sufficiently, thereby inadvertently raising relative humidity and increasing the threat to carriers, counter-acting the benefits of the lowered temperature

3.2.4 Temperature/humidity changes, as already mentioned in 3.2.1.1 above, can be more dangerous to carriers than stable, but sub-optimal, absolute values. Changes in temperature, but also in humidity, cause dimension changes, resulting in unnecessary stress to carriers. At highest risk are discs composed of different materials, e.g. lacquer discs, but magnetic tapes are also affected, specifically high density helical scan formats. The other basic danger is the possibility of condensation when bringing cold carriers into a warm environment.

Consequently, permanent storage conditions should be designed to have minimal temperature and humidity changes. During transportation, carriers must be protected by adequate logistics and containers (see 4.8). Changes of climatic parameters of longer duration require acclimatisation (staging) periods. For all materials, except lacquer discs, the temperature gradient should not exceed 3°C and the relative humidity gradient 5 percent points over a period of 24 hours. Additionally, to compensate for the different tensions within tape winds due to temperature changes (3.2.1.1), tapes must be relaxed by re-winding when bringing CA and PVC tapes to cooler storage conditions and PET and PEN tapes to warmer storage conditions. Lacquer discs, because of the threat of crackling due to different expansion coefficients between coating and substrate, are threatened by moves in both directions. Such transports should, therefore, be kept to the absolute minimum and be accompanied by long acclimatisation (staging) periods over several days.

The danger of condensation when bringing cold carriers into warmer areas must not be underestimated. Sufficient airing must be allowed until the carrier temperature is equalised.

Conclusions for the choice of climatic storage conditions. On the basis of the above discussion, it becomes clear that the choice of storage conditions is mainly determined by two conflicting principles: to keep humidity and temperature low (to retard chemical deterioration), and to avoid climatic changes (to prevent condensation and to minimise mechanical stress, most importantly for tapes and lacquer discs).

The minimum/maximum values to be kept to are:

As explained, the precise values between these maxima/minima, have no immediate negative or positive influence. However, in the mid- and long-term they determine the life expectancy of carriers. Of higher importance, however, is the stability of the chosen climatic conditions (3.2.1.1, 3.2.3, and 3.2.4).

For the purpose of storage recommendations, the following definitions are made:

¹ Permissible variations around the mean values are low frequency (annual) deviations.
² This mean value of “room temperature” condition reflects the situation in moderate climatic zones and is not necessarily obligatory for tropical countries. There, it may be prudent to choose a higher mean temperature, e.g. 25°C, and invest the saving in energy costs in effective dehumidification instead. This will also improve the well being of archival staff members, who generally may not find first-world climatic working conditions acceptable.
³ Permissible variations are low frequency (annual) deviations.

Please note: Temperature/humidity ranges and variability must not be added. The chosen mean value should be kept to the permissible variability.

Recommended storage conditions

The climatic conditions of studios and laboratories should be the same as, or very close to storage conditions. Whenever possible, work with carriers (e.g. routine inspection) stored at cool and low humidity conditions, should be carried out on the spot; otherwise, carriers must be adequately acclimatised.

The choice of target values for humidity and temperature is always a compromise between accessibility, comfort, and the health of operators on the one hand, and costs on the other. It must be further noted that even the lowest affordable values do not prevent, but only retard deterioration. Therefore, archives should choose those parameters that they can afford to keep 24 hours a day all year round. Within the permissible ranges, stability is more important than the absolute values of temperature and humidity.

Mechanical deformation is a major threat, which affects all kinds of audiovisual carriers.

3.5.1 Effects. Dust and foreign matter have a variety of effects on audiovisual carriers: with mechanical carriers they cause deviations of the stylus, resulting in audible artefacts (clicks). With magnetic tape, dust and foreign matter can clog the replay head and prevent intimate tape-to-head contact which, in audio, causes high frequency loss and, in video, the swift breakdown of the signal. With optical discs, the reading laser is obstructed which may lead to un-correctable errors and, eventually, muting.

Figure 25: Proportion of foreign particles of different size obstructing intimate tape-to-head contact.

3.5.2 Origin and prevention. One of the major origins of dust pollutants is mineral dust. This is a particular problem in arid countries. Archives in such locations must be equipped with tightly sealed windows and doors, which may need enhancement by air locks at entrances. Another prominent source in urban environments is textile particles. Carpeted floors as widely used in offices in the 1970s are, therefore, absolutely forbidden throughout the entire audiovisual archive. Floors should be of concrete, covered or sealed with chemically inert materials or lacquer, or of non-abrasive minerals (terrazzo-type). The floor should be of a colour that makes the typical local dust visible and does not camouflage it. Dust prevention is best achieved by mechanical filters in the air conditioning equipment. Additionally, a slightly higher pressure in storage and laboratory areas helps prevent the intrusion of dust into sensitive areas by creating an airflow out of the building through any cracks etc. in the walls.

Apart from minimising dust in storage and handling environments as a general measure, protection for individual carriers should be in line with considerations discussed in 4.7. Even under good general conditions, the residual risks of dust intrusion should be minimised by keeping the time that carriers are not in their appropriate containers during use as short as possible. LPs should be stored by having the inner and outer sleeve openings at different positions. In the absence of a disc, loading trays of optical discs players out of use must be kept close to prevent dust deposit that would contaminate discs.

Fingerprints make dust problems worse. They act as a glue for dust and provide nourishment for fungi. Touching playing surfaces with bare fingers must be absolutely forbidden: the use of lint-free cotton gloves is strongly encouraged. Special care is needed, when taking analogue discs out of their sleeves and putting them back, to avoid touching their surface in the grooved area. Turning disks around needs also manual skill and training.

Figures 26 and 27: Holding a disk without touching the grooved area.

Food and drink, especially sweetened soft drinks, are a major threat to all carriers, specifically to magnetic tape cassettes. Eating and drinking is, therefore, absolutely forbidden in all rooms where audiovisual carriers are handled or stored.

With magnetic tape, there are also problems that come from within the tape: dry abrasion (mainly with old CA tapes), exuded lubricants, and smear from hydrolysed tapes constitute major, internally generated obstruction to the replay of deteriorated tapes. Before their replay, such tapes need treatment and cleaning (IASA-TC 04, 5.4.3).

3.5.3. Air pollution, specifically industrial gaseous waste, can affect audiovisual carriers in many ways. There are indicators that suggest that heavy industry gases may have a negative influence on magnetic tape condition.¹⁷ It may be assumed, on the other hand, that environments that meet modern standards, which are set in the interest of human health, will not be immediately harmful to audiovisual carriers. Should archives be in the vicinity of industrial areas, however, it may be wise to consider appropriate air filtering. In addition, the exposure of materials to fumes caused by refurbishing work such as painting or gluing must also be critically considered. Appropriate measures have to be taken to avoid any (prolonged) exposure to such vapours. Finally, the residues from tobacco smoke build up on the surface of carriers and equipment, e.g. optical disc player lenses. This is another reason in addition to the risk of fire, to ban smoking, particularly in view of modern high data density formats.

3.5.4 Pests. Tropical areas, in particular, suffer from many forms of insects and pests which are difficult to keep out of laboratories and archives. Generally, most threatened are paper materials associated with audiovisual carriers, such as LP covers and liner notes. There is also a tendency for termites and other small bugs to creep into cassettes. No specific prevention can be given except keeping laboratories and storage areas as sealed as possible. Any chemical prevention should take possible interaction with carriers into consideration. Fumigation, as generally applied in tropical (paper) archives to fight insect affected paper materials, is discouraged because of the unknown possible interaction with carrier components, especially of magnetic tapes.

17. Professional video tapes from the same batch were stored under same temperature/RH conditions in Austrian TV archives in Vienna and Linz. The tapes from Linz, an industrial town with considerable air pollution problems at the time, suffered from significant pigment binder breakdown, the Vienna tapes did not. Although professionally investigated, the phenomenon could not be consistently explained.

3.6.1 Light and ultraviolet radiation have several deteriorating effects on audiovisual carriers. Many polymers, e.g. PVC, deteriorate under prolonged or permanent exposure to light. Extremely dangerous is the influence of light to the life of recordable optical discs (“dye discs”). Tests have shown that permanent exposure of such discs to daylight—and specifically direct sunlight—can render them unreadable within weeks.¹⁸ To what extent small doses of light over a period of years would influence such discs stored in their containers, but not in dark archival rooms, has not been explored. It is, therefore, wise to avoid any unnecessary exposure of all audio and video carriers to light, and to pay particular attention to ensure that any direct sunlight, which may also cause temperatures above safe limits, is inhibited.

Several audiovisual archives have installed low uv light systems in their storage rooms. This is a wise precaution particularly in busy archives where lights are kept switched on for long periods or permanently.

3.6.2 X-rays, as emitted from airport equipment, has, as opposed to undeveloped films, no influence on audio and video carriers. Tests have shown that extremely high, lethal doses used to decontaminate objects from germs such as anthrax spores, do not harm the recorded signals. It is not known, however, whether and to what extent such treatment may influence the further life expectancy of treated materials.

18. Kunej 2001.

Stray magnetic fields are the natural enemy of magnetic recordings. The susceptibility of magnetically recorded signals to deterioration up to erasure depends on the coercivity of the magnetic material—the resistance of a given magnetically orientated material to re-orientation. It also depends on the kind of the signal representation, which have varying sensitivity to partial erasure. The most susceptible signal representation is analogue (linear) audio recording. This also occurs on the (analogue) linear audio tracks of video tapes. FM audio, all video, and all digital signal representations are more resistant to distortion caused by magnetic fields. The permissible magnetic field thresholds are, therefore, given for analogue (linear) audio signal representations.

3.8 Cleaning of carriers.²⁴ In order to avoid the effects as described under 3.5, carriers must be cleaned to remove all kinds of foreign matter as well as residues and components of chemical deterioration. As a matter of principle, all carriers added to an archive should be cleaned before they enter the storage areas. This is particularly important for dirty/dusty collections from arid climatic zones as well as for carriers or whole collections affected by fungus. Before transfer, carriers must be checked again for dust, dirt, and other foreign matter and appropriately cleaned.

For all carriers (with some exceptions) the following sequence of action should be applied:

Compressed clean air. For infrequent application this is available in pressurised cans. For frequent use, a small compressor with an appropriate filter should be provided. 

Gentle mechanical wiping. For mechanical carriers, brushes with bristles softer than the materials to be cleaned, should be available for the careful removal of loose foreign matter. For tapes, soft lint free materials, e.g. pellon® fleece, which can also be mounted in the tape path, should be applied. For cassette tape, cleaning machines are marketed. Great care must be used with optical discs, as cleaning may often result in the production of unrepairable scratches.

Mechanical discs should be cleaned with an action that follows the groove. Optical discs should be cleaned with an action that is radial or across the signal track.

Health considerations must be observed when cleaning fungus from affected carriers and their containers. Such cleaning should be made in a chemical exhaust or fume cabinet or in open air, and operators must wear breathing masks.

Distilled water. Short exposure to water is permissible with most audio and video carriers. The exceptions include some instantaneous discs made from gelatine, cardboard, and similar water-soluble materials. To enhance the action, wetting agents may be added. For application with discs, washing machines are marketed. It is imperative that all carriers be thoroughly dried after the application of water.

Chemical solvents. Their application is the last stage for cleaning residue resistant to the more gentle methods from carriers. They must only be applied after consulting reliable sources and experts. As the composition of carriers, specifically historic tapes and instantaneous discs, is often unknown and their reaction to solvents unpredictable, careful testing must be done. It must be noted that unfavourable reactions may not appear immediately. Specifically the removal of chemical by-products of deteriorating materials must be carefully researched in cooperation with chemical experts. The use of commercial products with undisclosed ingredients is prohibited.

24 .This paragraph deals only with be basic principles of carrier cleaning. For details see the respective sections in IASA-TC 04, chapter 5.

The control of the environment in a storage area is a product of the prevailing conditions in the surrounding area, the construction of the storage facility, the quality of insulation and vapour seal, and the air-conditioning plant; when designing a storage environment all four of these must be taken into account. Overdesigning the air-conditioning plant to compensate for poor insulation, for example, leads to unstable and variable conditions. As has been discussed earlier in this publication, stability is more important than the absolute conditions being met. The following provides some general information that can be used in discussion with the appropriate design specialist.

Ideally, a storage area should be in the centre of a building, slightly elevated from the ground floor. Such a location would permit effective and autonomous control over all environmental factors, including temperature, humidity and water, dust and pollution, light, as well as stray magnetic fields. Any location at the fringe of a building would make such control more difficult, and possibly less effective. Any location lower than ground level makes air conditioning more expensive, and effective prevention of water influx difficult. Vaults should be fireproof, thermally insulated, and also protected against water influx, which may happen for a number of reasons.

Air conditioning, environmental control, or building management technology are all terms used to describe systems of varying sophistication that control and manage the environment inside a building. Though such systems were developed principally for the comfort of the occupants of buildings, they are a necessity if the rooms are to meet the long-term storage conditions of the audiovisual collections as specified in this publication. In principle, air conditioning systems are the same whether they are used for preservation and storage or comfort purposes. However, air conditioning systems for collection and storage demand much tighter tolerances and much better control.

4.3.1 Temperature control. Temperature control is achieved through heating or cooling the air that is being blown into the environment to be controlled. Sensors in the room detect the conditions and this information is used to control the heating or cooling elements. The interaction with sensors raises some issues that are discussed below.

It is important to note that cooling is the act of removing heat from an area and transferring it to another environment.

An evaporative cooling system, which passes air through a moist environment and so removes heat energy through evaporation, has no place in an archive, partly because it increases the relative humidity. In any case, it is only effective in very dry environments.

A critical fact in the design of environmental control systems is that heating air reduces the relative humidity and cooling air increases the relative humidity. Stable temperature and stable humidity are both of importance and their control is linked: for this reason all temperature control must be coupled with humidity control (3.2.3).

4.3.2 Principles of dehumidification. Almost all storage environments will require dehumidification most of the time in order to remove moisture from the air and so comply with the conditions specified in this publication. The need for humidification, the addition of moisture to the air, is much more rare and, if needed, can be achieved fairly simply. Relative Humidity, which is the most common way to specify moisture in the air, is a percentage measure proportional to the amount of moisture the air could hold at a given temperature and pressure, the latter being dependent on altitude.

Dehumidification is the removal of moisture from the air to reduce the relative humidity. As was stated above, cooling air increases the relative humidity. If the temperature of the air is made lower it will eventually reach a point at which the moisture in the air condenses to form droplets of liquid. The temperature at which the moisture condenses is known as the “dew point”.

Figure 30: Table of dew point levels. (By Easchiff (own work) [CC-BY-SA-3.0-2.5-2.0-1.0 (http:// creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons)

The most common way to dehumidify an environment is to cool the air being treated to a temperature well below the dew point and, thus, remove moisture from the air as water droplets. The treated air is then heated to the required temperature and the resultant relative humidity is a product of the amount of moisture removed by cooling and the final temperature of the air being treated.

This approach though practical, simple and common, has a number of significant problems. Firstly, the energy cost in cooling and then reheating air is quite substantial and should be considered as a factor in the long term running of any environment. Secondly, the amount of moisture removed from the air is proportional to the temperature differential and a system will often have to be overdesigned in order to be suitable for a wide range of environmental conditions experienced in many places. This is a particular problem in cool environments. And finally, it is very difficult to get accurate control using these sorts of systems, which may lead to cycling such that the system constantly seeks to adjust the conditions and this leads to regular increases and decreases in temperature and humidity, which is in itself detrimental to the storage of collection material.

Desiccant dehumidification is the removal of moisture from the air within a storage area by using a substance (desiccant) that is able to absorb moisture. The desiccant is subsequently heated, outside the controlled area to remove the absorbed moisture after which it can be reused. Such systems can achieve the low levels of dehumidification required for archival storage in most environments and are more energy efficient than the common cooling and heating approach described above.

4.3.3 Sensors are the devices used to detect temperature humidity and other aspects of air quality and condition. Most sensors used in an office environment have tolerances of ±5% or greater. While this is adequate when controlling office environments, when used in critical systems such as archival storage they cannot achieve the tolerances specified in this document.

Sensors detect the conditions in the controlled environment and communicate that information to the air conditioning system. In its simplest form, when conditions are outside of those required, the system switches on; when they are within required conditions the system is turned off. When the system operates in this manner the conditions in the controlled environment can cycle between high and low which has an adverse effect on the materials being stored. In order to overcome this, modern systems with high quality sensors and control technology gradually switch in and out heating and cooling elements leading to a very stable storage environment.

It is common practice to place sensors in the flow of air being extracted from the storage area. However, a poorly designed system can result in pockets or spaces within the storage environment that may be out of specification but undetected by the system (microclimates). Multiple sensors are recommended, with an appropriate agreement on how the sensors are weighted in determining the room conditions.

4.3.4 Air quality and filtering. Air conditioning systems are generally designed to recycle the air in an environment by adding a pre-set proportion of fresh air from outside. The smaller the proportion of fresh air, the simpler and more cost-effective it is to maintain the required conditions. The amount of fresh air is a health issue and most countries have standards that specify a minimum figure of around 10% fresh air. Though storage environment could have a lower proportion of fresh air this would necessitate sensors to determine the build-up of carbon dioxide and other unwanted gases in the storage rooms. It is also likely that the plastics in the media being stored will give off gases, which would build up in such an environment. Therefore, figures near 10% are a suitable compromise between cost and clean air. The flow of air through the room must reach every part in order to prevent any localised build-up of contaminants.

Pumping treated area air into an environment will almost certainly lead to a build-up of dust and other airborne particulates. Air conditioning systems must have filters that remove those particulates. The type of filter and the size of the particulates it removes will depend on the quality of the air both inside and, particularly, outside the building. In addition to well-maintained filters, the amount of dust in an environment can be minimised by maintaining a higher pressure in the room compared to the surrounding area.

For storage areas and laboratories, clean room classes ISO 8, preferably ISO 7 according to ISO 14644-1 should be the target.²⁵

The presence of sulphur dioxide, nitrogen dioxide and oxides of nitrogen, and other gaseous pollutants will degrade the life expectancy of the carriers stored in an environment. Most countries have a specification for air quality, and will recommend particular filter classes.

All filters require regular maintenance and cleaning in order for them to be effective.

25. ISO 8 equals clean room class 100.000 according to former US FED STD 209E, ISO 7 class 10.000.

The most effective way of controlling environmental conditions is to build a room with good thermal insulation and constructed with materials that are reasonably impermeable to the transfer of airborne moisture. Standard building materials such as stud plaster walls, bricks, and cinder blocks do not provide very effective insulation against temperature change and allow high levels of moisture to pass into the storage environment. If these materials are used, sealants must be applied to all surfaces, and all gaps, including around doors, must be sealed. The use of airlocks at doorways should also be considered.

One good way to provide a temperature controlled storage environment is to build an insulated envelope or structure within an existing building (4.2). The walls of such an envelope can be made from highly impermeable materials such as rigid aluminium and polystyrene sandwich panels as used to build food storage areas. All entry spaces including doors, electrical and other ducts, screw holes and fixing components must be sealed, as effective vapour sealing of the rooms is vital to their performance. Most places that use this type of building technology report being able to significantly reduce the size and cost of air conditioning plant. In the event of a disastrous loss of power, such storage environments maintain their conditions for a longer period of time.

It is often difficult to specify clearly to a builder or air-conditioning specialist the requirements for a storage environment. Merely stating the target temperature parameters may not produce a successful outcome. It is suggested that the following parameters be considered.

• Set point for temperature and humidity
• Tolerances expressed in values above and below the set point
• Frequency of change (the period of cycle between high and low)
• Rate of change (the gradient of the cycle)
• Amount of fresh air expressed in percentage of cycled air
• Air cleanliness expressed in terms of percentage, or the quality of filter necessary to remove that content
• Air flow throughout the room
• Number of sensors and their placement, and the means of determining the overall conditions
• Energy consumption under a range of conditions

An alternative to the standard supply contract is a performance contract in which the performance is defined in terms of given standards or approaches, but the supplier is commissioned over a given period of time to maintain and manage the system so that it continues to meet those standards. This is likely to be more expensive, but provides a strong incentive for the supplier to meet the specified conditions in the long term.

4.6.1 Material. Today, metal (steel) shelves are generally used. There is no risk in using them for storage of magnetic carriers (3.7.2.3). Wooden stacks, preferred in the 1950s and 1960s, are now discouraged as chemical treatment components may interact with audiovisual carriers.

4.6.2 Shelf loads. Shelves must be sufficiently sturdy to carry the load of audiovisual carriers. The approximate weight of 1 metre of carriers including typical containers is:

4.6.3 Storage position. All carriers, discs, tapes, and any cassettes should be stored upright. For discs, shelf separators should be in a distance of half of the discs diameter. Discs should not be tightly packed, however narrow enough to avoid permanent inclined position. Divisions for tapes are usually the same size of their diameter. During the absence of carriers in use, dummy replacements must be used to maintain upright position until carriers are returned.

Only soft, instantaneous discs, like gelatin or Decelith discs, should be stored horizontally in small piles with not more than 10 in a stack.

Ideally, carriers should be kept in chemically inert containers designed to provide sufficient protection against mechanical damage through normal handling and protection against light. With the advancement of conservation research over the past decades, the autocatalytic actions of several polymer degradation processes have been understood. Consequently, the use of airtight storage is not recommended as it could trap endogenous degradation by-products, thus increasing the rate of degradation. Generally, dust prevention should be achieved by proper insulation and air filtering of the entire storage environment. This will allow air to flow around the carriers which will help retard, if not prevent, autocatalytic deterioration. Where effective dust prevention of the entire storage area is not possible, a decision for carrier related dust prevention will depend on the relative risks of threats from internal changes in the carrier versus unavoidable external threats.²⁶

The materials preferred for containers designed to replace damaged or inadequate original ones are polypropylene and polybutylene for magnetic tape boxes, polyethylene bags or acid free paper sleeves for vinyl discs, and acid free paper sleeves for shellac records. For cylinder storage, the Association for Recorded Sound Collections (ARSC), in collaboration with the Library of Congress, has developed an Archival Cylinder Box²⁷.

Original containers or wrapping materials often suffer from a variety of problems: an acidic cardboard may have been used for tape boxes and disc sleeves; acidic paper for liner notes and booklets for LPs and CDs, as well as for inlays for notes for all kind of blank audio and video cassettes. In the early days of LPs, PVC sleeves were sometimes used which may cause plasticiser migration to damage LP surfaces.

Having optimisation of life expectancy in mind, ideally all carriers should be separated from inadequate original containers, wrapping and other accompanying materials. All such action should, however, be carefully considered and the improvements in storage conditions balanced against the financial and great organisational challenges such a task may demand. The great majority of containers and accompanying materials are themselves carriers of information that form a constituent part of the total document. Any loss or disorder through inappropriate cross referencing of separated parts of the document will generally cause much greater damage to the integrity and usefulness of the material than any theoretical optimisation of life expectancy. Generally, therefore, it is recommended that such exchanges be restricted to cases of obvious and immediate threat, such as PVC or other inadequate sleeves for LPs, or the removal of plastic bags from CA tapes.

26. Archives in moderate climatic zones may thus arrive at different solutions than those in hot and arid environments.

27. This container is designed for storing a single “standard-size” cylinder phonograph record. For details, contact Bill Klinger (Chair of the ARSC Cylinder Subcommittee) at klinger@modex.com.

Transport requires adequate measures against shock, climatic changes, and stray magnetic fields.

4.8.1 Shock prevention. The most shock sensitive carriers are cylinders and shellac records. These require adequate shock absorbing packaging, particularly when carriers are shipped by post or freight. Cylinder packing requires a careful balance between the prevention of any movement inside their boxes, movement of boxes inside outer containers, and appropriate measures for shock absorption. Additionally, attention must be paid to the prevention of elevated temperatures, specifically through unnoticed sun radiation. Because of their importance, transport of cylinders is often entrusted to art transport specialists (4.8.4). Shellac records require a box-in-box packaging. Inner and outer boxes shall be made from strong cardboard, separated in all directions by a layer of styrofoam or similar shock absorbing materials. It is imperative that discs inside the inner box are absolutely tightly packed to prevent any movement against each other. Vinyl discs are less shock sensitive, but an equal level of protection is wise to prevent damage to their covers. The same measures, particularly tight packing, are imperative for magnetic tape on open hubs to prevent any movement within the wind of the tape or movement of the tape pack on the hub or even slipping off the hub.

4.8.2 Heat and humidity. Any transport will expose carriers to climatic conditions outside optimal storage parameters. As a first measure, a method and routing of transport, including seasonal considerations, should be chosen to minimise these risks by avoiding exposure to extreme climatic conditions. Additionally, adequate packing must prevent unavoidable temperature changes and exposure to humidity. A typical threat is moisture penetration of carriers after long periods in cold environments and subsequent exposure to warmer and more humid conditions. Examples include transport in cargo holds of airplanes and landing in hot and humid climatic zones. Countermeasures include the provision of sufficient thermal insulation in the packing material during transport and, after transport, the carriers should be aired to prevent trapping high moisture levels and the temperature allowed to slowly return to normal. Whenever possible, audiovisual carriers should be transported in the cabin of air planes. Transport in unpressurised cargo holds should be avoided whenever possible.

4.8.3 Stray magnetic fields. The magnetic fields produced by metal detectors at airports for checking hand luggage are normally too weak to influence the recorded signals of audio or video tapes. As detectors for luggage to be carried in the hold may produce stronger magnetic fields, it is generally recommended that recorded magnetic tapes be transported as hand luggage. There is no information, however, on possibly dangerous stray magnetic fields with other transport systems, such as electrical railways, subways and buses, or other electrically driven transport machines. Such risks may be very low, as no incidents have been reported that would point to such sources of danger. However, in order to eliminate this risk, it may be advisable to protect magnetic carriers of exceptional value by carrying them in metal boxes of highly permeable materials.

A greater threat, however, may be the increasingly common electrically powered cars. Before concrete measurements of their stray magnetic fields are available, great caution is advised. It is important that tapes should be carried in metal boxes, or the use of such vehicles avoided until more is known about the possible dangers.

4.8.4 Cooperation with specialised transporters. The transport of large quantities of carriers, e.g. the relocation of whole collections, should be jointly planned and arranged with specialists in the field of transport of art treasures.

Disaster preparedness includes all measures to prevent, or at least minimize, the negative effects of unpreventable incidents of all kind, be they of natural origin, such as earthquakes and extreme weather conditions (which seem to be becoming more common in recent years), or man-made, like civil unrest, warfare, and others. The basic elements of disaster preparedness start with factors such as the choice of site for new archive buildings. A systematic search for any intrinsic dangers in existing archive buildings and their neighbourhoods should also be undertaken. Detailed plans to react appropriately in the case of unpreventable disasters will need to be prepared. These should have the protection of staff and visitors, as well as the survival of the collection, as the foremost principles to be considered.

A detailed discussion of disaster preparedness is beyond the scope of this publication. Environmental influences and specific preventive measures have been discussed in the respective parts of chapter 3. However, because of particular risks of fire and water to audiovisual carriers, these two aspects are covered here.²⁸ Finally, because of the absolute dependence on electric power, the necessity of an uninterrupted power supply in the case of disaster is underlined.

28. For general aspects of disaster preparedness, see bibliography.

Fire prevention and extinguishing must be given utmost importance. Beyond the safeguarding of invaluable material it must be understood that burning audiovisual carriers produce highly toxic fumes, which are of considerable risk to health. In addition to irreplaceable losses of holdings, complicated and expensive decontamination of premises may be the result of such incidents.

Ideally, the entire building housing an audiovisual collection should be separated into smaller fire divisions or zones of appropriate dimensions and equipped with a fire detection system. The walls, floor, and ceiling of each storage area should be fireproof and equipped with an automated fire extinguishing plant. In the 1970s and 1980s, Halon gas²⁹ was widely used as a fire-extinguishing agent for sensitive cultural materials. This was also recommended by IASA in 1981 (IASA-TC 02). Because of its effect on the depletion of the ozone layer, Halon and other fluorochlorinated hydrocarbon agents were banned in the Protocol of Montreal in 1989. Today, a number of more environmentally friendly Halon replacement gases are available for traditional materials as well as for server rooms of digital archives. These are also recommended for audiovisual materials.

The so called “dry fog” systems, that spray water in a very finely dispersed mist into the vault, are gaining popularity as the cooling effect is of great help with the protection of carriers exposed to heat from a fire, while water damage is very minimal. Such systems can be used for all kinds of archives. They are unsuitable, however, for electrical installations such as digital repositories (servers). Some archives are also starting to use low-oxygen storage, a technology that reduces the oxygen level in the air in the storage area below the point where a fire can be sustained.

Hand-held fire extinguishers should contain CO2. Water, foam, and powder, the most popular agent used in office-type extinguishers, must not be used. While chemically harmless, the removal of the fine dust of powder extinguishers from contaminated audiovisual carriers is extremely time consuming and is sometimes not possible to achieve.

29. Halon and its replacement gases extinguish fires in a concentration that is not dangerous for persons inadvertently trapped in a storage area in the case of flooding. Carbon dioxide (CO2) would be very effective and cheaper, but its use is strongly discouraged, often forbidden by legislation, because of the enormous risk for personnel, particularly in the case of false alarms.

Apart from keeping humidity low (3.1), special attention must be given to the prevention of water influx, which may come from a variety of sources. Storage areas should, therefore, be protected against water influx from all sides. This is most easily achieved if the store is located in an elevated position above the ground floor. A waterproof ceiling will prevent influx of water caused by plumbing leakages, heavy rainfall and water from fire extinguishing in upper floors. There should be no connection to the sewerage system, which, in case of floods, would be a path for influx. If an underground location cannot be avoided, careful consideration must be given to the prevention of influxes resulting from inundations, particularly in tropical areas, where storms can produce unexpectedly high amounts of water in a very short time. The installation of automated pumps may be advisable. In any case, materials should be stored some distance above the floor to help safeguard them for a period in the case of influx and give time for preventive actions to become effective. (For drying and cleaning flooded materials see 3.1.2.)

The operation of audiovisual archives depends on the availability of electric power. An uninterrupted power supply is essential for maintaining a digital repository and is also an essential for the operation of fire alarms and extinguishing systems. Even in technically highly developed areas, an uninterrupted power supply must always be a part of the respective systems. Additionally, to cope with the individual situations faced by developing countries, independent power supply units that produce sufficient power to keep the archive in operation in the case of frequent or prolonged black outs must be installed.

It should be kept in mind, however, that even in areas with normally reliable public power supplies, fire or unusual natural disasters will probably lead to power supply problems for which preventive measures must be in place. Most important is the provision of battery powered emergency light installations that will permit the safe evacuation of visitors and staff and assist the organisation during rescue measures. Additionally, depending on the necessity to keep equipment in operation, such as automated pumps to keep water out of storage rooms, adequately powerful stand-by generators with auto-starting mechanisms must be in place. These standby systems must be tested periodically.