night time temps in the 30's

Im about a week or so from going 12/12 and I have some concerns about how to keep my grow cabinet warm without the aid of lights. It holds heat pretty well, but its in an unheated area that may dip down close to freezing at times. I worry that 12 hours is a long time to go without warmth. I also have my fan on a thermostat so if the temp gets too low it wont supply any fresh air.
Can anybody offer some suggestions on what will work the best to keep the girls happy?

electric space heater with thermostat

Thats the obvious solution, but I was looking for something that would be a little safer to operate.

hmm. if you have an old computer, and arent worried about the bill. and have the room for it. plug it in, computers will heat a small area nicely. but just make sure its not too hot in there after.
in the summer i usually move my office into another room because upstairs with the computer going its wayyy too hot.

A small space heater is not dangerous. You can get one with a temp gauge built in

yeah those temp guage space heaters are as safe as it gets. only way one of those is fuckin up on you is some electrical arc or something. they're pretty safe.

boneman is right.theres no probs with the heater dude.

How about something like this: http://www.cheappetproducts.net/100_Watt_HEAT_EMITTER_Ceramic_Coil__30_to_40Gal_-P69296.html