gas leak detector used on boiler exhaust

dbsoccer

A friend loaned me his Toptes gas leak detector as he knows my house has a convoluted natural gas line that feeds a boiler and a gas log fire place. He found a leak on the inlet side of his meter and on a loose fitting on his propane grill and felt it would be good if I did some probing at my house. I've never smelled gas so never had a concern.

But tonight I took some time to try out the detector. Following the instructions I was unable to find any leaks in the many areas I checked. But...... when I probed the exhaust gas of my boiler the thing started beeping and the green light turned red and was flashing, etc. My boiler drafts out a side wall and I just happened to be outside walking by when the boiler was running.

I realize that most combustion processes are not 100% efficient and figured my boiler wouldn't be any different. So it didn't surprise me the detector detected combustion gas in the exhaust stream. But I thought I get the thoughts of the pros and other people more knowledgably than I am. Thanks in advance.

GGross

The flue is a direct path to the burner, which has gas because that's what it uses to make a flame. I sure hope you have combustible gas inside of your gas burner, or else it will not burn and you will be cold.

That being said if you want to safety check your flue you can use a low level CO detector near the flue to make sure it is not leaking any CO into the living space. In addition calling in a pro for service, and asking them to perform a combustion analysis, would allow someone to check your flue gases correctly.

dbsoccer

Thanks GGross. Yes I'm quite aware I have combustible gas inside the burner. That's not the question or concern. I was surprised, but shouldn't have been, for the detector to detect combustible gas in the exhaust stream.

captainco

Gas leak detectors are affected by temperature and moisture. They use a heated sensor. Any change in temperature can make them alarm. Moisture can make them alarm and also damage the sensor. You can't use them for flue gas!!

dbsoccer

Good to know. My intent was not to test the flue gas in any way, shape or form. I've done that with a combustion analyzer years ago which was when I discovered the contractor and plumber, during a remodel, failed to provide for combustion air into my boiler room. That was corrected long ago and the subsequent combustion analyze proved a success.

I only asked this question/concern as the detector went bananas when I placed it in the exhaust stream. So Captainco, your comments are helpful in understanding why. Thanks.

ChrisJ

I'd question the reliability of the detector now............