How to best use an oil filled heater?

i am using a grow tent and at night till around 9 or 10 in the morning the temperature drops below 40 degrees. i wanted to use a heater like this one: http://store.high-techoffice.com/hohzeloilfir.html
with a thermostat on it to keep the temperature stable. i was wondering if the heater is going to have to be on constantly, because of the fact that an exhaust fan is constantly pulling air from the tent? would it be okay to shut off the exhaust fan during the hours of cold so that the heater wouldn't have to constantly be running? should i have the oil filled heater inside the tent, or outside next to the air intake?

thanks.

Keep the heater and the fan on while it is cool out. It work by radiant heat, so is actually better than blown heat. Have the heater shut off 15-20 minuts before the lights come on, to let your ciruit cool down a bit. I have a mini oil heater on, and I love it. The circulation air picks up the heat, and the whole room stays nice and warm!

I havent used one in a grow room but i have on it my bedroom and they are awesome. It can throw a ton of heat all the way down to just a little. If i had to worry about keeping my room warm id use one.