Plugged heat exchanger causes high carbon monoxide levels

A plugged heat exchanger in a residential boiler raised carbon monoxide (CO) levels in a multi-family home, injuring four individuals.

The fire department’s incident report recorded a CO reading of 390 PPM in the home’s basement bedroom. It was also noted that the basement’s hardwired smoke and carbon monoxide detector had been removed.

The equipment involved was a small gas-fired residential boiler providing heat for a two-story residential home with a basement suite. Gas burners operate under a finned tube heat exchanger containing the water used to heat the home. The products of combustion pass through the finned tubes and up the venting system, then outside.


Clogged heat exchanger

The finned tube heat exchanger in the boiler had clogged up, preventing the proper airflow needed for complete gas combustion. The incomplete gas combustion produced carbon, further plugging up the heat exchanger, and carbon monoxide which spilled out into the living space.


Carbon and soot on boiler

The home owner said the boiler had not been serviced in over 10 years. The basement tenant said he removed the smoke/carbon monoxide detector thinking it was only a smoke detector and was going off without cause.


Smoke and carbon monoxide detector had been removed 

It is highly likely that the lack of equipment maintenance allowed the heat exchanger to plug up. In addition, the removal of the CO detector likely allowed the carbon monoxide to go unnoticed until symptoms became present.

The investigation is documented in BCSA’s enhanced incident investigation report format. 

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