How far should music electronics be from floorboard heater?

[gene12586]

I have a shelf with several levels which has all my guitar effects pedals on it, as well as my audio interface and preamp. It's standing not far in front of the floorboard heater in my apartment and the heat was just turned on. I'm curious how far away from the heater the electronics should be so that the heat doesn't harm the electronics.

Thanks!