I'm not the person who will say don't use a human heating pad--I use them for spares for individual tubs myself. However, if you DO use a human heating pad, there are things to consider.

First, make sure it does not have an automatic shutoff! Most heating pads these days DO. They will shut off after a few hours (or less). I had to search high and low to find heating pads without this 'safety feature'.

Second, do not set anything heavy directly on the pad or its cord--particularly not a glass tank. If you're using a glass tank, use short wood blocks or something similar to elevate the tank slightly ABOVE the pad. Otherwise, you will damage the pad which can lead to bad things, like fire.

Third, pay attention to the instructions on the pad which tell you to inspect it often for signs of degradation. When the pad discolors and starts to deteriorate, replace it promptly. I also use the cloth covers that come with the pads.

Control the heating pad with a thermostat or rheostat. The surface where the snake rests should be a nice 90 to 92F, no warmer, no cooler. The ambient temperature in the rest of the tank should be a nice 80F--if it isn't, you need a different heat source to regulate on the other side as well.