Natural Gas Leaks or Carbon Monoxide?

Distinguishing Natural Gas Leaks or Carbon Monoxide

Is it natural gas leak or carbon monoxide? While the two can coexist, the primary danger from a gas leak is fire and the primary risk from carbon monoxide is poisoning, including death. Gas leaks can be smelled by the human nose where only the most serious carbon monoxide leaks can be. 

By Rebecca Martin

It is not uncommon for the public to confuse the possibility of gas leaks with the dangers of carbon monoxide. There is still a misconception that one should be able to smell carbon monoxide (but see below). More importantly, it is often assumed that a gas leak rules out the presence of carbon monoxide. Gas leaks can occur with or without carbon monoxide and carbon monoxide can occur with or without a gas leak.

Gas leaks and carbon monoxide are often confused but while they may co-exist, the primary danger of a gas leak is fire or explosion, where the primary danger from carbon monoxide is poisoning.

Natural gas and carbon monoxide are both odorless. However, natural gas has an additive called mercaptan which gives it that distinctive smell. Mercaptan or methanethiol is an organosulfur compound which makes up a colorless foul-smelling gas often compared to the smell of rotten eggs. Although it is found in animals and plants, and even some foods, exposure to high levels of mercaptan can cause dizziness, lightheadedness, coma and death. But fortunately, it can be detected by people in very small quantities, less than one part per million.

Not everyone is able to detect mercaptan. There is a genetic mutation in humans that makes a very small percentage of people unable to detect mercaptan. But, in general it is an extremely successful sensory alarm to the presence of natural gas. Like gas it is also flammable and burns off during normal combustion.

If you are unable to smell mercaptan, there are other clues that might indicate a gas leak. You can use a gas leak detector. Gas leaks can produce stains or bubbling on walls. They can also produce a hissing sound. Leaks can be detected around the outside of your home by examining wet areas and puddles for bubbles.

One can also examine house plants for signs of gas leaks. House plants may be stunted or withered or even die. Humans can experience symptoms as well including severe headaches, memory issues, fatigue, loss of concentration, nausea and even suffocation. This can be the result of what is called natural gas poisoning.

Natural gas poisoning may have symptoms that are similar to carbon monoxide poisoning.

According to ADT, if you’re experiencing natural gas poisoning, you might experience:

• Ringing in your ears
• A reduced appetite
• Pain in the chest
• Nosebleeds
• Blistering or pale skin
• Flu-like symptoms
• Dizziness
• Breathing difficulties
• Lightheadedness
• These are some natural gas poisoning symptoms. You can experience some, all, or other gas leak symptoms. Your pets can also be affected by a leak. If they’re vomiting, having breathing difficulties, lethargy, or loss of appetite, they could be affected as well. https://www.adt.com/resources/natural-gas-leaks-in-the-home

Because there is less oxygen in the air, a gas leak can lead to oxygen deprivation.

Burns were the most common injuries, but inhalation also caused respiratory irritation, dizziness, and headaches. Most leaks are caused by natural gas utilities at pipelines, but some injuries come from in-home leaks.” https://www.frontpointsecurity.com/blog/gas-leaks-and-carbon-monoxide-buildup-causes-and-prevention

Monitoring your gas bill can also provide clues to the efficacy of your fuel-burning devices in your home. Sudden jumps in usage may indicate a leak. Gas stoves should be checked to make sure they are giving off a blue flame. A yellow, orange or red flame indicates that there is more gas than oxygen and there is a probability that there is incomplete combustion.

The Human Nose Can Smell Gas and Carbon monoxide

Natural gas and carbon monoxide are odorless, but only natural gas has an additive. This is because carbon monoxide is a byproduct of incomplete combustion, while natural gas is a fuel that is intentionally delivered to the source of combustion.

While carbon monoxide itself is odorless, incomplete combustion–the condition that leads to carbon monoxide–will also come with unburned hydro-carbons, i.e. smoke. Since natural gas burns quite clean, the smoke will be too subtle for the human nose to smell unless the levels get to be quite dangerous. In our experience, the human nose can start to smell unburned fuel when the levels of CO get to be something approaching 5,000 ppm in the exhaust. (5,000 ppm in the exhaust may equate to levels of 400-500 ppm in the ambient air as the levels get diluted when they enter the larger volume of room air.)

What is significant though is that dogs and other pets noses are so much better than humans, so they can smell the unburned hydrocarbons at much lower levels than humans. We believe that this is the reason that so many pets warn their humans that something is wrong in CO incidents.

Sometimes people notice a strange smell when turning on their furnaces for the first time in the Fall. Usually this is a slightly burnt smell which is a result of a summer of dust accumulation burning off and this odor dissipates quickly. This smell should last a very short period of time and if it continues for more than a few minutes, turn off the appliance and call your HVAC tech.

Other non-fuel related causes can produce smells and are related to worn out components, melting wires or overheating due to restricted airflow. These smells are often described as the smell of melting plastic or electrical and should be addressed by an HVAC professional.

There is a misconception that carbon monoxide detectors can also rule out gas leaks. But neither carbon monoxide detectors nor smoke detectors can detect the presence of natural gas in the air. Because it is assumed that it is more likely that the presence of gas will be detected by home residents, gas detectors are not typical to most homes. Homeowners can add more security by installing gas leak detectors in addition to smoke and CO alarms. There are also sprays one can use on gas lines to check for leaks.

How do most gas leaks occur? “Gas leaks often result from incorrectly fitted, poorly maintained, or faulty gas pipes and household appliances. If you don’t install your appliances properly, gas can leak from the seals or hoses connecting the cooker, boiler, HVAC system, stove, or other instruments to your area’s gas pipes and gas pipelines.” https://energysavings.com/blog/advice/gas-leaks-how-occur-what-to-do/#:~:text=Gas%20leaks%20often%20result%20from,gas%20pipes%20and%20gas%20pipelines.

An annual HVAC inspection and the proper installation and maintenance of all fuel-related appliances can go a long way towards eliminating potential gas leaks.

Last year I had an HVAC team come in and look at my older home and my gas lines were ultimately replaced. Local codes are normally updated on a regular basis as construction knowledge expands and safety issues are identified. The price for peace of mind is, in fact, priceless. They were also able to identify a problem with the gas line coming into my house which the utility company was quick to come out and address. This was extremely fortunate as the odd pipe jutting out of the ground was something I might have mistakenly attempted to remove and then found myself in a world of trouble. It is now safely buried and identified for any future residents.

Every year you probably receive notices from the utility company on how to avoid hitting a gas line. Some states, like mine, have implemented fines for failing to notify the utility company before excavating around your home.  However, gas lines can potentially leak or rupture. You might notice an area where the vegetation is dead or dying in an otherwise green environment. There may be a hissing sound, or dry or frozen ground, or water bubbling in wet areas or even a smell of gas. Major leaks may cause dirt or water to be blown up into the air or even signs of a fire burning below the surface. These are dire signs and should be reported immediately.

Evacuate if you Suspect Natural Gas or Carbon Monoxide

If you suspect a gas leak of any type, leave the area immediately, warn others away and call the utility company. Do not operate any devices in the area that could cause a spark such as cellphones, flashlights or a vehicle. Never attempt to extinguish any visible fire or shut off valves. Leave that to emergency services trained in gas leak response because it is flammable and explosive.

How does a gas leak produce carbon monoxide? As the gas builds up, the oxygen decreases, resulting in incomplete combustion.

“Incomplete combustion can occur when the gas mixture is richer than 10%. When this occurs, there is not enough oxygen to completely oxidize all the carbon-to-carbon dioxide. Some of the remaining carbon reacts to form the incomplete, less stable compound known as carbon monoxide. “ https://www.pinedalegas.com/natural-gas/hazards-of-natural-gas#:~:text=At%2075%25%20gas%2C%20a%20person,in%20a%20matter%20of%20minutes.

Carbon monoxide can result, and unlike natural gas poisoning, carbon monoxide poisoning can become fatal in a very short period. While both natural gas and carbon monoxide can produce flu-like symptoms at lower saturations over a period of time, carbon monoxide rises to its role as an apex predator quickly as oxygen levels decrease. While natural gas can be volatile because it is flammable and can cause natural gas poisoning, carbon monoxide is the leading cause of death by poisoning in the United States. Natural gas can cause oxygen deprivation and the resulting symptoms, carbon monoxide interacts with the hemoglobin in your body causing permanent damage to major organs such as the heart and brain.

One of the main differences between natural gas leaks and carbon monoxide is injury or death from natural gas leaks are rare. However, more than 400 Americans die of carbon monoxide poisoning every year, more than 100,000 visit the emergency room and more than 14,000 are hospitalized.  Yet we still hear “I didn’t smell gas”.  What is important is to remember that gas leaks and carbon monoxide can go hand in hand to create tragic circumstances and understanding the warning signs of both is important. While the presence of carbon monoxide doesn’t always indicate that a gas leak is present, the presence of a gas leak always has the potential to produce carbon monoxide.