https://ball-pythons.net/forums/show...Quarantine-Tub
Welcome to the forums! Above is a link to jmcrook's quarantine tub set up, and shows an excellent example of using a CHE with a smaller tub. My house also gets cooler at night but with appropriate sized CHEs I have no issues keeping my enclosures the right temp even if the temps in the room drop below 75. As far as your concern about a fire hazard using a CHE, I'm not going to tell you that they couldn't start a fire, but if you use them correctly the risks are pretty low. I've had CHEs running literally for years with no issues. As long as you're using a thermostat and the appropriate fixture you should be fine.