Not necessarily an electromagnetic field that could cause damage, but I would be more wary of static electricity generated from the high velocity flow of air from the vac. I know my own ShopVac in dry conditions can build up a whing ding of a charge that I usually get when I get near the power switch to shut it off.
arcaxis is correct.....I used the wrong terminology when describing why a vacuum is dangerous around micro-processors. It's the static. I actually recall times when replacing PWB boards and or chips that we wore wrist bands with static discharge clips on them to avoid damaging the components. I assume that's still the case today??? Not sure.