Rob Falke, National Comfort Institute president, takes a carbon monoxide reading on a gas furnace during a training opportunity. CO readings above 15 pmm are considered dangerous, though many CO detectors don’t even register at such a low level.

Carbon monoxide (CO) testing is one of the main concerns that should be addressed in every structure in which contractors perform work, if not for the safety of the customer, for their own safety. The fact is that total CO safety testing by contractors probably takes place less than 10 percent of the time. Is it because there is too much liability in doing testing? Maybe technicians just don’t have the time on each call? Could it be that technicians don’t need to test to determine if there is a problem?

A comment recently made by a business owner to one of his service technicians was that he didn’t want him to test because every time a CO problem is found it creates a controversy and it is giving the company a bad reputation. The industry often talks about educating the consumer, but when is this going to happen if contractors don’t know the real story? Let’s look at the history of CO testing and equipment for some insight.

Unless a contractor owned a commercial or industrial combustion analyzer, electronic carbon monoxide testers were not available or affordable until about 1990. Prior to that, most CO testers, primarily glass tubes, could only determine if conditions were deadly or not at that particular moment. They provided very little diagnostic information.

Now digital CO test equipment has been available for 17 years. What did people read to brush up on how to use these testers? Whether they went to engineering school, vocational school or some other HVAC training there was almost no information written on proper CO testing. Most digital CO test equipment is supplied with a manual that tells little on how to perform a complete CO diagnostic test or what the CO readings indicate when you find them.

Unfortunately with the new equipment came the same old misconceptions: Blue flames don’t make CO, if you have CO you probably have a cracked heat exchanger, CO always has an odor or it usually makes soot, and check for moisture on the windows. In the year 2007, I think it is way past the time to get the CO story straight. Often I hear the comment, “You are preaching to the choir.” To this I reply, “It would have been great if you had spent a few bucks on singing lessons first.”

To know how important CO testing should be, it would be helpful to know what level of CO in the air can start affecting a person’s health. Levels outdoors above two or three parts per million (ppm) have statistically shown a significant increase in hospitalization for asthma and congestive heart disease patients. CO does not have to be present in high levels to cause permanent damage, disabilities or chronic low-level CO poisoning.

The World Health Organization lists 15 ppm of CO as the first level that can affect people. CO levels close to 30 ppm are listed as causing health problems in much of the population. It is a medical fact that babies, children, and the elderly are affected by low levels of CO. From Sudden Infant Death Syndrome, Alzheimer’s, Parkinson’s, Attention Deficit Disorder, loss of hearing, loss of sight, loss of speech, kidney disease, respiratory disease, heart disease, etc., the list of CO related illnesses seems endless.

After reading many articles about people that have been diagnosed or treated for the flu or other illnesses by doctors, who then end up dying from CO poisoning, it might be said that the medical profession may not be as aware of the problem as they should.

Recent news articles have mistakenly advised the public that even though CO sickens many people, only a few are ever in need of treatment. CO has a half-life of four hours, which means any time someone is exposed to CO, it can do damage for many hours after. If treated in a hyperbaric chamber, however, it can be totally removed in 90 minutes.


Obviously, contractors cannot control outdoor conditions or medical misdiagnoses. On the other hand, however, when it comes to fuel-burning appliances and other hazards to which customers may be exposed, contractors should accept this as their responsibility. If the gas oven kills the customer, the contractor still loses a customer. It would seem logical that every contractor should provide their customers some type of CO educational material and definitely promote the use of CO alarms, especially low-level monitors that protect everyone.

There are many possible sources for CO in a home. Furnaces, boilers, and water heaters are often thought of most commonly. There are also, however, space heaters, gas logs, gas ovens, gas dryers, and fireplaces. It doesn’t matter whether a company services the equipment, technicians can still do a safety check.

In addition, educating the customer on the dangers of all gasoline-powered equipment, including vehicles, is very important. All year long there are stories in the news about people getting CO poisoning operating gas generators during power outages. Operating a vehicle in or near the garage can cause a high buildup of CO in the house.

There are many ways for contractors to address the potential CO hazards to which their customers may be exposed. In addition, there is money to be made doing this. What may end up being unusual about this situation is that when the customer pays this time, they might actually say, “Thank you.”


Are there any visual signs of a potential CO problem? Yes, there are, but by no means should this ever be substituted for actual CO analysis. Corrosion of burners, heat exchangers, drafthoods or flue pipes is a key indicator that an appliance is not venting properly. Equipment not venting is the main cause of flue gases and CO getting into the building. Soot buildup is a definite sign that CO is being produced, but it does not indicate any predictable level.

The unit can have soot and be making 200 ppm of CO and it could have no soot and be producing over 4,000 ppm of CO. Discoloring of cabinet doors and panels, melted wires or controls, and moisture dripping from flues are sure signs of a potential CO problem that may exist or could occur. Obviously a pile of used matchbooks next to a standing pilot appliance isn’t a good sign either.

Because of constant changing environmental conditions, an appliance could be producing deadly levels of CO one day and then not repeat this operation for days or weeks. Therefore, even a CO test can be misleading if we don’t know how to interpret the information.

Is CO testing creating more liability? The only way doing carbon monoxide testing can be a liability is if we do it without the proper training or think we already know all there is to know.

What are the acceptable levels of CO that appliances are allowed to produce? Which CO readings are the most dangerous? When should equipment be red-tagged and disabled? Are the remedies for a problem a true fix, a cover-up, or more dangerous than the original problems? Does replacing equipment solve problems or create new ones? Not knowing the answers to these questions could jeopardize the health and safety of every customer.

Publication date:06/11/2007