HP 20/700 - Manual (Page 162)

Appendix A DLT Drives and Tape Cartridges 161
Appendix A
DLT Drives and Tape Cartridges
Caution Potential cartridge damage: Tape temperatures above 49° C
(120° F) might damage the tapes. If during storage or
transportation a cartridge has been exposed to conditions
exceeding the above values, before using the cartridge, keep the
cartridge within those operating environment specifications for at
least as long as the time that the cartridge exceeded the
specifications, up to two hours. Make sure that the cartridge has
no moisture on it.
When storing DLT cartridges, the stray magnetic field at any
point on the tape shall not exceed 4000A/m. Make sure that the
cartridge has no moisture on it.