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Saturday, October 31, 2009

Furnace Odor

I have a Duo-therm furnace, model #90130.001 and when the propane tank gets almost empty, the furnace gives off an awful gas odor in the RV. Is there anything one can do to eliminate this odor?
Ned, (Jonesborough, TN)


Ned, the LP odor seemingly emitting from your Duo-Therm furnace when the container is almost empty is not typically attributed to the furnace itself, but rather the level of fuel in the container. 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.

Liquid propane is inherently odorless and colorless and as potent as LP is, the odorant is added as a safety feature. 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 odorant can seep into the appliances and become evident to the user.

In furnaces, this phenomenon is usually kept to a minimum since the furnace is a completely sealed system and uses outside air to mix with the LP for combustion. But it can happen since the 900 series Duo-Therm furnace utilizes a different type of burner configuration which forces an extremely rich mixture into the combustion chamber. If any unburned fuel is left inside the chamber at any time during the heating cycle, the smell could be evident inside the RV. You probably do not have a problem as long as you do not smell the mercaptan at other times when the container holds a greater amount of LP. To be sure though, I recommend you have your coach thoroughly leak tested using a manometer.

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