Electrical Heaters for thermal cycling tests

Good morning, i am writing because i would like to ask you for some more information about heaters. In short, we have a chamber and we are going to do thermal cycling tests inside of it. 

For this purpose, we need to bring the temperature in the chamber from -35c to +50c. 

To warm up the room we need to choose electrical heaters with a small thermal mass and that are safe for temperatures around -35c and resistant to moisture. Of course, we will make the heaters work at 0c and not at lower temperatures. 

Could you please help me to figure out the most suitable solution? Thank you in advance.