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What is the difference between carbon monoxide and a gas leak?

Gas leak image; carbon monoxide


With the freezing temperatures outside, we can be assured that winter has finally arrived in Chicago.  Now that furnaces are running, we are often asked to investigate the possibility of elevated carbon monoxide or a gas leak in a client’s home.  Many clients have a tendency to confuse these two health hazards.  Let’s review the origin of each hazard and how to avoid elevated levels in the home.   

Carbon monoxide is a product of combustion, or to be more precise, improper combustion.  The health hazards associated with this is asphyxiation and possible death.  This improper combustion can occur from furnaces, gas or wood fireplaces, water heaters, and poorly maintained gas stoves and ovens.  On one assignment, I discovered that the elevated level of CO was due to the owner warming up her car in the attached garage.  It would be better to pull out of the garage before letting your car warm up.  Because this carbon monoxide is colorless and odorless, we advise having a carbon monoxide detector operating in the home to alert you if there is a danger.  We also advise:

  • keeping gas appliances clean and well maintained
  • ensuring combustion venting is intact and exhausting to the outdoors
  • avoiding excessive negative pressure, which can prevent combustion gases from exhausting

A gas leak is pretty straightforward; it’s a leak of natural gas from a pipe serving a combustion appliance (furnace, water heater, etc.).  The primary constituent of natural gas is methane, which is an odorless, colorless gas that is difficult to detect through our five senses.  That is why a tracer gas is added (known as mercaptan) to help detect the location of the leak.  Although it’s possible that people can develop health symptoms (headaches, etc…) from a leak, the greatest danger is from a possible fire or explosion.  The best form of prevention is to sniff around the gas lines of your house and see if you smell anything out of the ordinary.  Some of our clients have thought that they were smelling mold or sewer gas when in reality they were smelling the mercaptan gas.  Mold has a more musty odor, whereas mercaptan has more of a sulfur or rotten egg smell.  If you suspect anything, give your local gas company a call and ask for someone to come out and inspect the property.  Typically the gas company does not charge to come out and inspect the possible leak.

Both of these issues have harmful, if not lethal, effects on one’s health.  It is to your advantage to take the proper precautions and ensure healthy air. 

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”

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