Hi again HVAC-Talkers,

My wife has a severe (potentially fatal) allergic reaction to the sulfur compounds added to natural / propane gas to make it smelly. Because of this we want to be very, very careful that there is not unburned natural gas or combustion products making it into our indoor air from the the older Rheem 90% furnace that heats our home.

I am in the process of selecting a new contractor for our routine HVAC maintenance. With the unburned gas side of the equation I plan on asking them to "check our gas lines for leaks with a detector sensitive to 1 ppm". Is there any sort of standard test used to see if there are leaks between the combustion side of the heat exchanger and the indoor air side? If so what is this test called?

[One of these years maybe we'll find ourselves with lots of money and can switch to a nice electrically powered geothermal system that will avoid the issue entirely...]