The Mr Heater "Buddy" heaters do not require venting. They are part of this latest generation of "safe" heaters that have a built in oxygen depletion sensor. It shuts off when it senses low O2 levels (or is it high CO levels?).
I have used one of these for camping both in my tent at Cruise Moab and in my FJ45 Wagon. Worked great in my tent. I have run them on both the large cylinders (put outside with extension hose leading in) and the 1lb er's. I have a 4lber that I will use in the tent after using a Hazmat leak detector. I am not as concerned about venting fumes in the tent. In the Cruiser they heat so well on the low setting in the small space that I wake up in the middle of the night and shut it off, then wake later and turn it back on. More concern about the sensor working right in the Cruiser.
Only issues I see are that it (mine) does not have a tip over shutoff switch. I worry that due to wind or other factors it may tip over and I wil be so tired from wheelin that I may not wake up in time.. I always secure it on top of a non flammable, metal container. Other issue is that it is designed to work directly off a cylinder without a regulator. It has a small orifice to limit the amount of fuel it can take. This can also clog, they make filters available to put inline, I suggest anyone using one of these heaters to get one.

Hope this helps!

Eric