G'day all,

Among other things I picked up an old 2.5HP window A/C that was short on refrigerant from Ebay (.99c) to cut up and experiment with.

The first thing I did was to recover the R22, braze on some service valves and charge it up with propane. When the propane went in it *stank* of Ethyl Mercaptan.

I checked the MSDS from the supplier and it's supposed to be >95% propane with ethyl mercaptan and a few trace hydrocarbons. Checking the PT in the bottle it looks pretty close.

Now the oddity.

I ran the A/C for about 30 minutes playing with different charge levels and then left it for 2 weeks. When I went to recover the gas today I noticed the smell of ethyl mercaptan had completely gone. The only noticeable odour was the mineral oil.

Now, the reason I made this observation was I've seen a number of web pages where people have either charged splits, or DX heat pumps with ducted heads with BBQ propane. Most of them have made the assertion that if it leaked they'd know about it from the smell.

To follow this further I whipped up a 50/50 mix of propane and isobutane and put it in my car A/C. Drove around for a couple of hours (the unit was originally R12 and "retrofitted" with 134a). Not only was the cooling *far* better, but again when I checked the gas there was *no* smell.

Something in the refrigeration process is removing or breaking down the Ethyl Mercaptan.

Just a heads up.