Safest way to increase tent ambient temperature?

[Toomuddy]

Safest way to increase tent ambient temperature? I don't want to use devices such as the buddy heater

 

[Aussieadventurer]

A diesel heater is you best bet here. The arm air it produces is moisture free and no fuel is burned inside you tent therefore the air stay completely safe

 

[Tom Davis]

Yep, a diesel heater should do the trick. Check out the one from Planar