And as has been pointed out before, the combustion process depends on having enough oxygen;
if plenty of oxygen;
propane + oxygen ---------> carbon dioxide + water
but if not enough you may get a mixture;
propane + some oxygen -----> carbon monoxide
+ carbon dioxide + water
the same goes for butane although the chemical formula of butane is slightly simpler, but it makes no difference to it's being burned and the products produced.
Carbon monoxide is odourless and colourless and locks onto the red pigment in blood blocking it from carrying oxygen around the body. Once locked on it is very difficult to remove and the body is starved of oxygen - this can lead to death. It is a silent killer.
Get it checked by a registered gas engineer for safety's sake. Do not use until it has been checked.
Check out these links;
one BBC, one American but VERY relevant as it deals with motorhomes and RV's.
Your local Trading Standards should have a list of registered engineers for LPG, or ask at a dealer that does habitation checks. Don't leave it till later.......