I snagged one of those to see how it does in my space. I have it set up outside my 5x5 tent with it blowing in through one of the small ducts near the bottom of the tent. The air blowing out of it can be uncomfortably warm if you keep your hand in front of it for any length of time. And I’m careful to make sure any leaves I’ve clipped/dropped aren’t near the hot air very long. While I don’t think the incoming air is hot enough to start a fire, I don’t want to take chances.
My ambient temp in the basement is about 68F and I’m able to reach 81-83F with this heater, though it runs near constantly on level 8 of 10 during lights on. IMO this heater is basically at its upper limit of space heating in a 5x5. Also I’m not sure I’d expect it to heat more than 20-30 degrees F above ambient temp.
All in all, it’s doing at least as well as 3x ceramic bulbs in reptile heaters clipped to the top of the tent, though I’d really like to see it cycle more versus running almost constantly.