As I understand it, the compass needle is magnetized so that it will point to the large iron deposit in the earth, the magnetic north pole, which is near the earth's true north pole. Compasses are regularly stored & carried in proximity to other products made of ferrous metal all without apparent effect. Compass manuals do not warn of any such hazard. Indeed vehicular compasses are made with adjustments for biases due to nearby steel & electromagnetic fields. In normal use compasses do not seem to be particularly susceptible to permanently biased readings due to minor storage influences. I'm a lot less confident about what happens when they're subject to powerful magnetic fields.<br><br>When taking compass readings, it's a good idea to test for how much influence the steel products you're carrying cause. Moving the compass towards & away from metal items indicates their range of influence. Knives, multitools, handguns, magazines, & long guns are commonly carried influences. The influence seems to dissipate around 6" from the ferrous metal object. YMMV.<br><br>You may want to try your own experiments. BSA stores offer a number of inexpensive books on compasses & orienteering. A lot of other vendors such as REI, Sports Chalet, & Cabela's carry similar materials. <br><br>John