Re: electricity & fan motors
Do you notice problems when going from a hot temp outdoors into a cool air conditioned building? The other reaction could be thermal variance causing shock (reaction) to the body.
With the blowers/compressors and Flourecent tube lighting used in those isles it's possible those are triggers for you. Compressors/alternators/generators generate a mild-light magnetic field if you are right next to them due to the motor. However those are burried and are not close to where the person is in most setups.
If it was electricity your moniter gives off a field as well as the computer tower. The transformer in the PC generates a field as does the moniter or if you have a Tube TV (not todays "thin" TV's). That gives you two other potential areas of conflict.
I'm still thinking it may be thermal for primary reason.