Contractor inspecting residential water heater.

Sources of Carbon Monoxide in the Home

In Articles by Elizabeth OrtliebLeave a Comment

Poorly maintained heating appliances can be sources of carbon monoxide in the home. In fact, residential carbon monoxide poisoning is the most common scenario for CO [carbon monoxide] exposure, accounting for most non-fatal injuries and almost half of deaths caused by CO.

Importantly, homeowners are at a heightened risk for carbon monoxide poisoning during the winter months, and a regular heating inspection (at least annual) should be a priority in order to ensure properly working equipment and their personal safety.

Thus, as an HVAC professional, you play an important role in preventing residential carbon monoxide poisoning. And, it starts with informing your customers and potential customers about the sources of carbon monoxide in the home, which is the focus of this article. Let’s get started.

Carbon Monoxide is a “Silent Killer” in the Home

Carbon monoxide is called a “silent killer” in the home because it is a poisonous, colorless, odorless and tasteless gas. When this gas is breathed, it displaces oxygen in the blood and deprives vital organs of oxygen, which can lead to injury or even death.

You should be aware that most cases of residential carbon monoxide poisoning occur in the winter and while people are asleep. In particular, you should recognize that ill-maintained heating appliances can be sources of carbon monoxide in the home.

The danger of faulty heating appliances should not be ignored, and preventative measures should be a priority for HVAC residential technicians; however, there remains a lack of understanding about such measures by homeowners.

For instance, consider this fact: According to a 2011 American Housing Survey, less than half of occupied U.S. households have a working carbon monoxide alarm. While this number is concerning, there is a redeeming static: More than 60% of respondents in a 2006 Healthstyles Survey about carbon monoxide safety agreed that furnace maintenance is important.

As an HVAC professional, this should make you recognize the important responsibility you have in communicating the danger of faulty heating appliances to your clientele. Because of this important responsibility, we’ve decided to provide you with a simple way to explain the sources of carbon monoxide in the home, which leads us to our most important point:

Heating Appliances That Are Potential Sources of Carbon Monoxide in the Home

Carbon monoxide is a concern for those home appliances that burn fuel, such as natural gas or oil. In fact, carbon monoxide is produced when there is incomplete burning of fuel, the burner is improperly tuned, and/or the appliance is malfunctioning. It is one of the common combustion pollutants, along with nitrogen dioxide and sulfur dioxide.

The sources of carbon monoxide in the home can be from vented combustion appliances and unvented combustion appliances.

Vented Combustion Appliances

Vented appliances are appliances that carry combustion pollutants outside the home and include furnaces, hot water heaters, and gas clothes dryers. If such appliances are not properly installed or poorly maintained (e.g., blocked or leaking venting system), a carbon monoxide leak in the home can occur.

Unvented Combustion Appliances

Unvented appliances do not vent to the outside and include oil-fueled space heaters along with gas cooking stoves and ovens. With these appliances, combustion pollutants can be released directly inside the home. Additionally, if other unvented types of appliances, such as gas grills or portable generators, are improperly used inside the home, then there is a risk for high carbon monoxide levels.

See the handy figure we’ve created below to see the potential sources of carbon monoxide in the home:

Common sources of carbon monoxide (CO) in the home.

The average home has 4-6 fuel-burning appliances that produce carbon monoxide (CO).

While all common household combustion appliances normally produce carbon monoxide, it does not usually pose a risk to household occupants unless the appliance is malfunctioning or not vented properly. The amount of carbon monoxide produced depends upon the type of appliance, the kind fuel it uses, and how well the appliance is installed, maintained, and vented, which leads us to our next point:

Ensure Residential Combustion Safety with Proper Maintenance

As an HVAC technician, you have an important responsibility to help prevent carbon monoxide poisoning in the home, and that’s where Bacharach can help. We offer a full line of combustion analyzers and carbon monoxide monitors for residential technicians, including the Monoxor Plus, the Fyrite InTech, and the Fyrite Insight Plus.

Insight Plus Combustion AnalyzerThe Monoxor Plus is the perfect instrument if you need to monitor carbon monoxide in ambient air or stack gases, and it includes a trending graph with real-time value displayed, minimum and maximum measured values, and ability to log a 15-minute CO ambient test. The Monoxor Plus can be particularly helpful for measuring ambient concentrations of carbon monoxide immediately upon entering the room where a heating appliance resides.

Or, perhaps, you are needing an instrument for complete combustion analysis? Check out our Fyrite InTech, which measures O2, CO, stack and air temperature for complete combustion analysis. Looking to measure draft/pressure as well? Then see our Fyrite Insight Plus, which is our most advanced combustion analyzer for residential technicians. With it, you can measure stack pressure/draft to determine proper venting and to make sure that combustion gases (including carbon monoxide) are being vented up the stack properly and not backing up into the boiler.

Have the Right Instrumentation Along with You

Ultimately, you must ensure safe operating conditions and determine combustion efficiency when installing and maintaining household heating appliances. If you inform your customers of the potential sources of carbon monoxide in the home and have the right equipment along with you on your service calls, you will see a measurable difference. 


How do you help ensure good indoor air quality and prevent carbon monoxide poisoning? Let us know by leaving a comment below.

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