alarm

I fitted one a while ago & found it quite confusing:
1. Is carbon monoxide heavier than air?
Carbon monoxide has a density that is about 97% that of air under normal room temperature. So, to answer the question, no, it is lighter than air. You would think, then, that it would rise. In real-world conditions, there are a lot of forces that cause the CO to mix rather completely into the air. Therefore, it will neither rise nor fall. What might be more important is the temperature of the gases it is part of. Since it is a combustion product, the hot exhaust gases that contain the CO will rise, but are soon mixed into the air you are breathing. If there is a source of CO present, such as a poorly-maintained stove, the CO level will highest close to the source, and decline with distance.

I found another reference that suggested 5 feet from the floor was the best position.

My instructions say around shoulder height

Many toxic gasses are heavier than air, LPG is, and in workshops where vehicles are running a deep pit contains exhaust gasses (NOx) which are heavier than air. That kills blokes who are in a deep pit. The gas may rise a bit when hot with convection but cooler they sink.

I have bought one and will install it about ankle height in the van, definitely below the mattress level.
If you don't hear from me anymore then I may have that wrong.

Why just CO rather than CO2 and or LPG?

What type is best and where do you get one?

Thanks

Because it mixes with air and does not sink like carbon dioxide and LPG, around seated head height would be a good place. I note someone has said the instructions on theirs said should height (standing I presume).

Last winter I posted a My Blog on heating on the dangers of carbon monoxide. Worldwide, thousands of deaths each year are attributed to carbon monoxide poisoning.

My understanding is that the trigger point for the alarm is set well below the lethal concentration of CO. It should therefore give plenty of warning before you become drowsy / head-achy, etc and while you are still able to take the appropriate action.

Given that CO mixes with air, rather than building up near the floor or rising to the roof, the recommended height of near shoulder level would seem sensible.

We always sleep with the door vent and top vents open, thus reducing moisture levels and therefore condensation as well as reducing the chances of any buildup of harmful gases.

Cheers
Andrew

consi the shoulder height instruction is probably in a situation where people are expected to be standing ...... think about how that works when sleeping.

where ever you have it, will be better than none

cheers

I had a van for a while but never heard about needing a CO alarm and would probably question as to why one is needed when there is always air flow able to get into the van via an external vent or vents in the door or behind the fridge which I believe the door vent should not be able to be closed I may be wrong..

I would be more inclined to install an LPG gas monitor in a van.