There is more to carbon monoxide safety than leaky furnace heat exchangers. Venting problems may actually cause more CO safety issues than leaky heat exchangers. I am not suggesting that you overlook the importance of checking furnace heat exchangers for leaks, but rather that you expand your CO safety horizons a bit. I want to talk about CO safety concerning the technician – you. A combustion appliance operating in an unsafe condition can spill vent gasses containing CO out into the room where it is operating. This can create a safety hazard for technicians going into that area to service the furnace. You should carry a CO detector that displays the CO level in the area you are working in. If the ambient CO goes above 50 ppm – you should leave. 50 ppm is the OSHA standard for the maximum allowable concentration for an 8 hour work day.
Ray Wohlfarth recently published an article in the October 2015 issue of Plumbing & Mechanical magazine in which he discusses a story of an electrician being overcome by CO fumes. The electrician was working in a mechanical room on something completely different than the boilers, but the boilers were in that room and not operating properly. When the electrician failed to report back to the school administration, the secretary was sent to see what was taking him. She found him passed out on the floor – ran and called 911 to get emergency medical help. This undoubtedly saved his life. Suppose that had been a service technician working on a furnace with nobody home? By the time someone found the tech – it would probably be too late.
Before you go to a big box store to get a home CO detector, consider that they are typically built to UL 2034 standards, which allows 15 minutes before alarming at levels above 400 ppm. This is just not fast enough in the case of high levels. The UL standard is weighted to prevent false alarms, but this also means that a UL listed device can fail to alarm at dangerous levels until it is really too late. Plus, typically these do not show what the CO level is. Kidde, a primary manufacturer of these types of CO monitors, points out that their devices are for continuous monitoring – not short term detection.
Single gas, battery operated CO detectors which display the CO level are available for $100 - $150. Alternately, you could use the CO setting on your combustion analyzer. If you don’t have a combustion analyzer, you could put that $150 you would normally spend on a single gas CO detector towards one of the lower cost $500 combustion analyzers. You will be doing both yourself and your customers a favor.