I use one all the time for taking my little boy. They are great products. When we shoot woodys I’ll pop up a blind right by the hole and keep him in there with the heater and an iPad while I’m setting up he stays in until right T shooting light then stands with me.
I use the 4,000 to 9,000 Mr. Buddy heater in my 17ft camper, I have a carbon monoxide detector and its never went off, the heater has a built in sensor as well, I run it off of a 20lb tank with a hose, if the temps are above 35 I have to crack a couple of windows two or three inches to keep the heater from running us out, even on low. Works great !