What Does Carbon Monoxide Smell Like? The Silent Killer in Your Home

Home safety is more than just having locks on your doors. Carbon monoxide is an odorless, colorless gas that can cause house fires, negative health effects, and even death. 

Even worse, it's the byproduct of several normal household activities, like running a car or building a fire. 

Source: Henry & Co. on Unsplash

We'll cover common sources of carbon monoxide in the home, why it's dangerous, and the best ways to protect yourself and your family from exposure. 

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What Does Carbon Monoxide Smell Like?

Like other mammals, humans have a fine-tuned sense of smell to help us avoid poisoning substances. Unlike gasoline or spoiled food, however, humans are unable to detect carbon monoxide by smell. This is what makes it so dangerous. 

The Odorless Nature of Carbon Monoxide

Since carbon monoxide is odorless, it's more likely to go undetected and slowly poison the people exposed to it. 

CO is formed from one carbon and one oxygen molecule. It's a byproduct of incomplete combustion. This means that when a substance burns (like the fuel inside a car or the wood in a fireplace), some CO is produced. This also makes it highly reactive with other substances.

Because of its simple molecular structure, neither humans nor animals can smell carbon monoxide. It doesn't contain anything that triggers our olfactory sensors. 

Just as something lacking any pigment would be processed by our eyes as "colorless" or "clear," carbon monoxide lacks a noticeable smell. 

Source: Wikimedia Commons 

Why Carbon Monoxide is Called a "Silent Killer"

Because of its simple molecular structure, CO doesn't have a noticeable smell or taste. That wouldn't be a problem, except for the fact that carbon monoxide is highly dangerous. 

According to one study, carbon monoxide poisons cause over 100,000 emergency room visits per year, and over 400 deaths annually. People die from inhaling this gas each year, and many more become sick or are hospitalized. 

Clearly, something that is undetectable by human senses and highly dangerous is a threat. It's vital to learn the sources of CO, the best way to detect it in your home, and what to do if you suspect CO exposure. 

Common Misconceptions About Carbon Monoxide Odor

Although it has been well demonstrated that carbon monoxide is odorless, there are several myths that persist:

Myth #1: "I can smell carbon monoxide": Impossible. No matter how sensitive someone's nose may be, there are no scent-producing atoms in CO. You are likely smelling other chemicals that it is mixing with, like gasoline fumes.

Myth #2: I will only become ill if exposed to very high levels of carbon monoxide. Untrue. Exposure to CO at levels of 70 parts per million or higher leads to symptoms in most people - those with heart and lung problems will likely feel sick at lower levels. 

Myth #3: Only homes with natural gas need to worry about CO. Carbon monoxide can be created by a wide variety of household actions - grilling, fireplaces, cars, and using a gas stove. 

Read on for a complete breakdown of CO sources around your home and what to do about them. 

How Can You Detect a Carbon Monoxide Leak?

Every home should have a carbon monoxide detector. It's also helpful to know the signs of CO poisoning, because you might feel sick before the alarm sounds. 

Source: Martin Splitt on Unsplash

Signs and Symptoms of Carbon Monoxide Poisoning

Carbon monoxide poisoning often mimics the symptoms of the flu. 

Symptoms include: 

• Trouble breathing

• Chest pain

• Nausea

• Headache

• Dizziness 

• Fainting or loss of consciousness 

• Confusion

• Vomiting

Trace amounts of CO can also cause symptoms that develop more gradually. If you're experiencing any of these symptoms, immediately call 911 and go outside. 

The Importance of Carbon Monoxide Detectors

One straightforward solution is to make sure your home has a working CO detector. Just like with household smoke alarms, these systems are designed to alert you with an annoying noise if they detect CO indoors. 

Remember, people cannot tell if there is carbon monoxide in the air - even at high levels. A CO detector is absolutely essential. 

Don't forget to install one anywhere you'll be spending significant time, including an RV, cabin, or boat, along with your primary home. Ideally, having one in your garage is vitally important, since car exhaust systems release CO.

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Other Indicators of a Possible CO Leak

Sometimes it can be hard to find the source of a CO leak. Here are a few other tell-tale signs that can signify the presence of a CO leak:

• Unusual condensation on the windows near gas-powered appliances 

• Yellow, weak, or flickering pilot lights. This can indicate incomplete combustion, which produces CO

• Soot buildup or unusually discolored areas near your gas appliances

If you notice any of these signs around your home, seek help immediately from a qualified technician to inspect your appliances. If at all possible, stay elsewhere until your home has been inspected. 

Source: Wikimedia Commons 

What Are the Common Sources of Carbon Monoxide in Your Home?

The risk of CO is so high because there are many appliances around our homes that produce this odorless and tasteless gas. 

Here are some of the most common culprits.

Gas Appliances and Heating Equipment

Natural gas is a relatively cheap and abundant heating fuel, and is used by many homes across the country. In fact, around 61% of U.S. households use natural gas for at least one heating source. 

Source: U.S. Energy Information Administration 

Gas-powered appliances in your home could include:

• Furnace

• Heat pump

• Water heater

• Stove 

• Washing machine 

• Dryer

• Generator

• Space heater 

Leaks from any of these appliances - even small ones - can cause carbon monoxide poisoning. 

Vehicles and Outdoor Power Equipment

CO outside can easily leak indoors if you have an attached garage. Or, if you spend a lot of time with your vehicle, inside the garage or shed, or operating lawn equipment, you could be exposed to CO. 

Blocked Vents and Chimneys

Most gas-powered appliances have a mechanism that vents CO outside for safety. 

Similarly, fireplaces - both wood and gas - produce CO. They need to be properly vented through a chimney so that CO doesn't have a chance to build up in the indoor air.

It's crucial to have your home's vents and chimneys inspected regularly to ensure the air is safe. Many people also choose to place their CO detector near the fireplace to make sure it catches any leaks right away. 

How Can You Prevent Carbon Monoxide Leaks?

As with many household hazards, an ounce of prevention is worth a pound of cure. Take early, regular steps to handle possible CO in your home, so you don't leave yourselves exposed to the toxic fumes. 

Regular Maintenance of Gas Appliances

It's generally recommended that fireplaces, chimneys, and gas-burning equipment be inspected every two to three years to ensure they are working properly. 

If you are a homeowner, be sure to schedule these inspections regularly. If you're a renter, be sure that regular inspections are part of your lease, otherwise your landlord could be in violation of safety laws. 

Inspect pilot lights regularly for irregular flame or soot buildup, which are both indicators of incomplete combustion and CO production. 

Proper Ventilation in Your Home

Ensuring proper airflow is another way to keep your home safe. 

• Install carbon monoxide detectors - you'll need one on each floor of the home and near all sleeping areas

• Keep chimneys and vents free

• Never operate a grill or generator in a garage 

Safe Operation of Generators and Charcoal Grills

Gas generators can be handy in a power outage or when operating certain tools, but they can be deadly if used incorrectly. 

Here are a few guidelines for properly using generators to minimize the risk of CO production:

• Never operate a generator inside or in a garage

• Keep a CO detector nearby when using

• Allow the generator to completely cool down before refueling and restarting 

• Continuously monitor the generator and turn it off when you're not using it. 

Similarly, grills are another one of our notorious carbon monoxide sources. 

• Only use the grill outside

• Keep it clean

• Keep a CO detector nearby

• Never grill while under the influence

• Never leave the grill unattended 

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What Should You Do If Your Carbon Monoxide Alarm Goes Off?

The first step to take if you hear your CO detector's alarm is to evacuate the area. While you may be driven to try to find the source of the leak, the first thing you should do is to get fresh air and minimize your own exposure to the gas. 

Remember, exposure to carbon monoxide can cause long-term brain damage if medical care is not received promptly. 

Immediate Steps to Take

The first thing to do is go outside. Be sure you bring all pets outside with you - they can't smell carbon monoxide either, and the last thing you want is to return to the home only to find the family cat didn't make it. 

If everyone feels fine: call your gas company. They generally will dispatch a technician right away if CO leaks are suspected. 

If anyone in the home is exhibiting ANY symptoms: call 911. Emergency personnel will bring specialized carbon monoxide detectors with them that can trace the amounts in the area. They will also check your family for serious health conditions that might require hospitalization. Remember, some symptoms of CO poisoning appear very mild - like dizziness or headaches - but can be life-threatening, especially in the very young or elderly. 

After you've called 911, be sure to call your gas company too so they can begin to inspect your home and find and fix the leak quickly. 

When to Call Emergency Services

You should always call 911 if anyone in the home is experiencing any symptoms of CO exposure. Remember, these include symptoms that can easily be confused with the flu or other viruses. 

Of course, if anyone loses consciousness for any reason, you should always call emergency services or take them to the nearest ER. 

Follow-up Actions After a CO Leak

One of the characteristic signs of CO is that you generally feel fine once you leave the exposed area. This can be a good way to tell the difference between exposure and the flu - if you really have influenza, you won't feel better just because you got some fresh air.

If you need to evacuate your home because of carbon monoxide, don't reenter until authorities say it's safe. 

Furthermore, be sure that emergency services or technicians have disabled any appliances that were causing the leak. DO NOT use those appliances again until they have been repaired and inspected, or replaced entirely. 

How Often Should You Check Your Carbon Monoxide Detector?

Detectors don't last forever. Generally speaking, they last between 5 and 7 years. When you install your CO detector, it's a good idea to write the expiration date on the unit itself with a permanent marker. 

Recommended Maintenance Schedule

As with fire alarms, you should check your carbon monoxide detectors every six months to ensure proper function. 

Most units have a "test" button that you can press to ensure that it's working correctly. 

Signs That Your CO Detector Needs Replacement

Some signs that it's time for your unit to be replaced include:

• The test button does not function correctly

• The unit is beeping

• The unit is past its expiration 

• Where to Place CO Detectors in Your HomeINs

Most state laws mandate that a carbon monoxide gas detector be placed within 10 feet of all sleeping areas in the home. You should also place them where CO gas producing appliances are used, like grills, stoves, and fireplaces. 

Source: Erik Mclean on Unsplash

Conclusion: Protect your Family from the "Silent Killer" 

While you may not die from CO poisoning, it has been shown to lead to severe health damage. It's estimated that between 10%-40% of survivors suffer some kind of permanent neurological damage. 

You can protect your family from CO exposure by:

• Installing CO detectors throughout your home

• Monitoring appliance usages

• Being especially aware in the winter months, when most accidents with CO occur

• Immediately evacuation at any signs of CO exposure

By taking the threat seriously, you can reduce the risk of suffering health consequences from this common, but deadly gas.