IMO a co2 detector is a must item if using a Buddy or not. It's way too easy for a near by vehicle exhaust to enter you vehicle, or your own exhaust for that matter. When I used a more sensitive detector, you would be surprised how ofter this happens without your knowledge.
Exactly!
Except, it's CO (carbon monoxide), not CO[SUP]2[/SUP] (carbon dioxide).
Gasoline engines output massive amounts of carbon monoxide, enough so that an exhaust leak that gets through the firewall or floor of the vehicle can kill you while you are driving, not to mention being parked next to a vehicle that's idling. If you drive a gasser, having a CO detector is critical. It doesn't matter if you have a Buddy heater or not. I mean, if you have a propane heater, you
gotta have one, but you
need one, anyway.
A diesel engine outputs carbon monoxide, but at a level that is virtually non-existent (less than 1% of that by a gasoline engine). However, as RoadTime notes, you can have an idling gasser parked right next to you with its CO exhaust coming into your vehicle, and a CO detector could save your life. Big trucks who always park with the big trucks don't necessarily need a CO detector, but they're so cheap that it wouldn't hurt to have one. I have been in the parking lot of a chicken processing plant, parked and sleeping for a few hours waiting to get loaded, and my detector went off. It was from the processing plant.
You don't need to install it in any special place, just in a place where there is decent air flow (not in a drawer or cabinet). The specific gravity of regular air is 1.0, and the specific gravity of carbon monoxide is 0.9657, so they essentially the same density, anywhere the air flows is fine, could be high or low mounted.
If you have a propane heater, then you should probably consider a dual detector that detects both carbon monoxide and explosive gasses (propane, natural gas methane, etc).