I posted this question in a earlier thread concerning the tragic death of a child who was using a propane heater while deer hunting.

I just happened to check the operating instructions for my Little Buddy Propane Heater and found it states that a minimum fresh air opening of 4 square inches (example 2" X 2" opening) is required for safe operation. Again, this is the minimum for the Little Buddy heater and not their larger models.

Pretty much have a window open. With a window open you shouldn't build up carbon monoxide to any kind of level that could be toxic.

I thought they had a cut off switch.

I keep a window open anyway.

I believe the buddy heaters do have a cut off to prevent CO poisoning, but i cant say that is true for every propane heater out there that soemones grandpa used in 1975....

A friend of mine died, about 25 years ago, from a propane heater he was using on a Montana elk hunt.

When it comes to the discussion at hand, the terms "cracked" and "open" can mean different things to different people, which can result in different size openings. Some might even use the term "cracked open" to describe how they make sure a window in their box stand or ground blind is left to avoid carbon monoxide poisoning. The purpose of my post was to share something that would apply to all of these.

Chemistry was never my strong suit but I have to wonder if the type of heater doesn't also come into play. For example, I have a metal heat drum for my old single-burner Coleman stove that makes a good heater for use in a deer stand. I've been told these were quite common with folks up North when ice fishing and before catalytic heaters became available. Could be wrong but I suspect heaters that use an open flame are the worst in creating carbon monoxide.

As for open-flame combustion, they create almost exactly the same amount of water vapor and carbon dioxide as catalytic or ceramic heaters do, but open-flame combustion (like on a stove top) burns less efficiently. Whenever you see a flame that has a yellow or orange fringe, that means the combustion process is incomplete,m so you're not getting all the heat you could out of your pound of propane; worse yet, that inefficiency means the flame is creating deadly carbon monoxide. I'm OK with using a ceramic (e.g. Mr Heater Portable Buddy and others) heater, which burns very efficiently and has an entirely blue flame once it warms up, but I'd never use an open flame or stove-top flame, which always have yellow or orange fringing for space heating.

Thanks for sharing. I've seen open flame, propane burners made for frying fish and turkeys in large pots used to heat camp houses. Doesn't sound too safe after reading your comments.