Ed Rose, left, a mechanic for Knight's Airport Limousine of Shrewsbury, and Evan King, a field service engineer for Roush CleanTech, prepare a Knight's passenger van for a propane tank installation.

Propane is a source of heat and power for many motorhomes and travel trailers. While it typically lasts a long time—especially in appliances such as refrigerators—propane will eventually run out. When ...