3.7.1 Magnetic field thresholds

For medium coercivity iron oxide pigments, as typically used for analogue open reel audio recordings (coercivity around 400 Oe (Oersted)) the maximum permissible field strengths have been determined to be:

5 Oe (= 400 A/m) AC
25 Oe (= 2000 A/m) DC

These thresholds have been set at 50% of those levels where influences of magnetic fields on pre-recorded audio tape have become measureable. Chromium and metal tapes have a higher coercivity.