Propane gas

I can always tell when my propane tank is about to give out by the distinctive odor that permeates the house. I am curious as to why this occurs. There is never an odor until the tank reaches aproximately 10%. I used to blame it on excess gas bleeding through the standing pilots, but have updated all the appliances with thermocouplers so that can’t be the problem. The odor persists even without using any of the appliances in question.

I have thoroughly checked all fittings and orifices for any leakage and found none.

Anyone know the why of this? Even wildass guesses appreciated.

From http://www.rvdoctor.com/rvdoctor259.html

“A chemical odorant, ethyl mercaptan, is induced into liquid propane during the distilling process to insure that if a leak occurs, the user would indeed be made aware of it. … Since the mercaptan is heavier than the liquid propane, it eventually settles to the bottom of the storage container. When a container is near empty, the percentage of mercaptan relative to the remainder of the liquid fuel is far greater than normal. When LP is utilized in RV appliances as a vapor during this low level situation, some of the smell can seep into the appliances and become evident to the user.”

Thank you there funneefarmer. I knew about the addition of mercaptain, but not the fact that it was heavier than propane.

Great Cite, what did you use for a search query?

I used http://www.google.com

Narrowed it down by putting the following in the search window.

“propane”+“empty”+“smell”+“mercaptan”