Is Your Home Vulnerable to Carbon Monoxide? Does Your Home have Combustion Issues?

Do you have combustion appliances in your home? This can be a gas water heater, or a gas cook top or a fireplace burning wood, or combustible logs or propane or natural gas. A combustion appliance can be a gas powered clothes dryer, or an actual wood stove, or a gas or propane or oil furnace. We need to include coal here, charcoal, and woodchips and pellets…

If you are using a combustion appliance, you have a potential problem with carbon monoxide.

Carbon monoxide is odorless, tasteless and invisible and is a by-product of all types of combustion. And carbon monoxide, if not properly vented up a chimney, will make you and your family sick- flu like symptoms and when the concentration is high enough, cause victims to go comatose and die.

More than 400 people die each year in the United States of carbon monoxide poisoning. Many more frail people have been made frail by low levels of carbon monoxide poisoning, or made sicker by CO poisoning. Flue like symptoms at low levels of poisoning can be easily mistaken for just ill health until the poisoning is stopped.

What are the Symptoms of Carbon Monoxide Poisoning?

The effects of carbon monoxide are a progressive increase in dizziness and nausea and then listlessness and unconsciousness and then death. Impaired vision and coordination, headaches, dizziness, confusion are all possible symptoms. Low concentrations over time, which are not detectable by most CO detectors (more on this next)  can give you flue like symptoms and cause fatigue in healthy people and chest pain in people with heart disease. These can clear up if these same people leave the area of chronic low concentration of Carbon Monoxide.

Low levels of Carbon Monoxide poisoning can make frail and sickly people much more sicky and even kill them. Elderly people and asthmatics can be severely impacted by carbon monoxide and the problem is not differentiable from the symptoms they are already suffering from.  At higher concentrations, impaired vision and coordination; headaches; dizziness; confusion; nausea. Can cause flu-like symptoms that clear up after leaving home. Fatal at very high concentrations.

We will first talk about how to prevent carbon monoxide exposure – cover the issues that can help create it and then we will cover the monitoring of carbon monoxide in the home.

The traditional way to get carbon monoxide poisoning was through a damaged combustion chamber. It makes sense to have furnaces with combustion chambers checked for leakage by professionals on a regular basis. Combustion chambers are under strain from heating and cooling can crack and release combustion gases into the air stream and distribute Carbon Monoxide through your central air system. This is the traditional way that you could be affected by carbon monoxide. Make sure you have your furnace or your gas powered heat system checked on a regular basis.  This can be a life saver.

OF SPECIAL NOTE – Beware of Ventless Combustion Devices

Avoid any type of heating device that does not vent combustion gases. Ventless fireplaces are dangerous and can be deadly. Ventless fireplaces are described as all the fun of a fireplace anywhere without the expense and hassle of a real fireplace. Nonsense, they might warmth but they add carbon monoxide.

More practical for heat when you are cold, but just as deadly are ventless kerosene or propane heaters. These are often used is what feels like an emergency. Be careful, they can be deadly. Wood smoke is quite aggressive and will drive you out of the house if your damper is closed or the chimney is not venting right. But propane or even kerosene releases Carbon Monoxide and carbon monoxide is tasteless, has no odor and cannot be seen. Now most people know this, but a reminder is helpful, and maybe some of you had not really registered this information.

Modern or retrofitted homes can increase risk of Carbon Monoxide poisoning

As modern homes get more air tight to keep moisture and unconditioned air out, you get fewer natural air exchanges with the outside. This can cause more stagnant air and allow a concentration of any carbon monoxide problem you might have. In the recent past, leaky windows and walls, and floors and ceilings allowed conditioned air to quickly leak out everywhere and, while certainly not ideal for comfort, made Carbon Monoxide poisoning much less likely because of the air leaks.

If you have a tight home, or if you go through a professional effort to create a more air tight home, emphatically if you are using combustion appliances, but it makes sense to also make sure your home also has a system for mechanical ventilation, which is a system to bring in fresh air through planned points of entry and not just random air leaks when the weather is cold or hot and the doors and windows are closed. Have you ever considered where your fresh air comes in from?

But beyond dealing with humidity and moisture issues, and household odors in tight houses, tight homes can also be a factor in negative pressure inside your home. Fireplaces and water heaters are expected to evacuate combustion gases, thee combustion gases are hot and lighter in density than the room air and are expected to float right up out of a chimney. But if your home is tight, there can be a lack of air to replace these combustion gases and you create negative pressure and the gases will not leave your home. This air for proper evacuation of combustion gases is called make up air. Modern homes and kitchen remodels also might utilize powerful range hoods to evacuate cooking odors. The newest homes are being built to new ventilation standards that require makeup air for appropriate combustion appliances and powerful fans, but in the transition many homes can have issues with make up air. You will have to do some self evaluation of your home to determine if these issues need further consideration.

Do you have a powerful range hood in your home, or a centralized vacuum cleaner system, and a clothes drier and bathroom fans, other kitchen fans… below is a graphic of potential appliances in your home- that vent air out of your house.

Venting air to the outside is an issue even if you do not have combustion appliances.
Depressurization in your home that is creating more pressure for air leaks and helping create negative pressure inside your house. You comfort is being impacted, your power bill is frittering away money because you are heating and cooling the great outdoors, and who knows what is being sucked into your home unnecessarily.  Further discussion here. Are your HVAC supply ducts leaking? Are your supply ducts leaking as well as being in the unconditioned attic? All kinds of issues can manifest themselves here.
You can spot the various appliances here that are sucking. On the left I think there is a built in shop vac? I must have stolen this from another Yankee. Not many North Texans have a furnace in the basement. but a furnace in an air handler? yes. Know your combustion appliances.

Can you  spot the various appliances here that are sucking? On the left a built in shop vac, in the hallway a built in vacuum system. On the right, dryer venting and a kitchen range hood. Bathroom fans. I must have stolen this image from another Yankee. Not many North Texans have a furnace in the basement. but a furnace in an air handler? yes. Know your combustion appliances.

Venting air out of your house requires make up air to take the place of the air your fans are blowing out. You are creating a negative pressure situation and air in most homes just sneaks in through air leaks for make up air.

So, the right combination of fans working together can potentially create a negative pressure in your home that could allow a carbon monoxide to linger in your home and impact your family.

You can have a professional test for these conditions; you need someone certified in CAZ – Combustion Appliance zone testing. Here is usual information from the state of Texas on CAZ.  A CAZ technician uses instruments to test for a worst case negative pressure zone in your home. You can also monitor any CO in your home. More later on that subject.

Is your HVAC - air handler in the garage?
Is your HVAC in the garage? Automobile exhaust and Fumes from stored chemicals, fuels, etc. which you store in your garage can be sucked into leaky return air ducts and drop carbon monoxide as well as other contaminants into the house. Mechanical issues are discussed here.

Now don’t make the increased risk of Carbon Monoxide effects an excuse for not tightening your house. Carbon monoxide risks must be removed anyway; there is no safety factor in a leaky house. Getting the air leaks out can prevent moisture problems and health issues that can be a part of moisture problems in a home. Get the air leaks in your home sealed up. This makes for healthier homes. Air leaks are the source of moisture problems and all kinds of unhealthy stuff flourishes in moist environments.

Are you at risk? Is  your home at risk?

First off, you need to understand that you must have combustion appliance burning to be at risk for carbon monoxide.

If you are concerned you can monitor for possible levels of carbon monoxide.


the average CO meter on the market is pretty stupid and will only test for temporary conditions- basically to prevent sudden high levels of carbon monoxide that could prove fatal. These types do not detect low levels of carbon monoxide over time which is needed to detect chronic conditions that might make people ill or more ill. The manual for most CO detectors will have a disclaimer for the elderly, the sick child or pregnant women. Make sure you understand exactly what you are getting with a carbon monoxide detector.

Any questions, any comments add them below.

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