Question about propagation heating pad

I have a propagation heating pad that goes under the 10"x20" tray. I do not have a thermostat for it. Is it safe to use on top of carpet in the house with the tray dome and little plants on top or will it get too hot on the carpet? I was also thinking of putting the pad and tray in my non heated grow room in its future drip tray home. Will it get too hot on the 2'x4' plastic growing tray? I don't want to start a fire. The non heated area still gets in the 30 degree F at night.

lol, i use one of those sore muscle heating pads. i only use it with a dome for cuts. the trick is using the dome vent holes to dangle a temp gauge in to make sure you don't cook em. if it's too hot, i just fold the towel over the heat pad (thicker/thinner) until i get the temp right. i'm not paying $70 for a friggin pad and thermostat... i'm cheap!