Understanding Carbon Monoxide Red Flags in the Home

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While carbon monoxide gas (CO) is itself undetectable to the senses, carbon monoxide red flags in your home are visible if you know what to look for. Colorless and odorless, CO is a byproduct of combustion ranging from a wood fire in the fireplace to the kitchen stove to a gas-fired furnace burner. It’s also in the exhaust of internal combustion vehicles and small engines like lawnmowers and electrical generators. Approximately 450 Americans die from carbon monoxide gas every year—many in their sleep, having gone to bed totally unaware that CO from some source was silently filling the house. As many as 8,000 each year have to be hospitalized due to exposure to the gas.

Carbon Monoxide Detectors

The most important safeguard against the potentially fatal effects of CO is the proper number of functional carbon monoxide detectors in the home. In most residences, one detector per floor plus one in or immediately outside every sleeping area is recommended. Annual tune-up and evaluation of gas-fired systems, particularly the furnace, water heaters and stove, by a qualified professional is also recommended.

Other Carbon Monoxide Red Flags

Because the difference between the concentration of carbon monoxide gas that will sicken versus the amount that will rapidly kill can be quite small, it’s also important to remain alert for carbon monoxide red flags such as:

  • Soot or smoke streaks on or around gas-fired appliances indicating inadequate venting or backdrafting.
  • Noticeable moisture and condensation forming on interior walls and windows. Excess water vapor, a byproduct of combustion, in indoor air may signal an obstructed furnace vent or water heater vent.
  • Rust on the furnace flue or other vent pipes in the house is another sign of inadequate exhaust gas venting.
  • Burner flame in the furnace, water heater or stove that is yellow or orange. Any color other than blue is indicative of incomplete combustion, which may be generating excessive CO gas.
  • Fireplace smoke entering the house due to insufficient upward draft in the chimney.

Contact the professionals at Apollo Home Heating, Cooling, Electrical and Plumbing about any potential carbon monoxide red flags you may notice in your home.


"Ernie & Mike did a superb job on my new furnace and A/C installation. Despite having more than a day’s work to do, they came in and stayed until the job was done. They were organized, efficient, and protected the rest of the house well. Got both furnace and A/C installed the same day. Ernie was courteous, informative, and clearly knew his job better than anyone I’ve encountered before. The units look so good guests now get The Tour of our new system. Apollo is clearly not a fly-by-night company. I would recommend them to anyone in need of a new furnace and/or A/C."
- Jerry A.
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- Cassandra B.
"The team at Apollo exceeded my expectations. As a business owner, my attention to the details and commitment to providing excellent service is high. From the sales rep. to the installation team, everyone’s performance was outstanding. For example, the installation team went to great lengths to protect our floors, placing floor runners and across the wood floors and up the stairs. They even were spot washing walls upon their departure. I highly recommend this company."
- Randy B.
"We scheduled an estimate AND a tune-up. We knew something was wrong with our furnace, but hoped we could make it through the rest of the season. Upon telling Bill what our furnace was doing, he warned us immediately what the possible outcome was going to be; a cracked heat exchanger. He watched the flames roll backward, tested carbon monoxide levels, which were so high they meter’s last reading was 5,600 before saying “high”. He immediately shut it down, tagged it, and explained that with levels that high and children in our home he wanted off right away. He continued his inspection and showed us via a camera that not only was it cracked in multiple places, but had holes all over it. He gave us a few options for repairing it; his knowledge as well as genuine concern was beneficial and refreshing. Luckily we also scheduled an estimator, Micah, to come too and we were able to get costs between repairing and replacing (with several options). We decided to replace with a much higher efficiency furnace and one sized properly to our home. Hands down, not only did they both provide us great service and knowledge, but without sounding dramatic, they may have saved our lives. This was our first time calling Apollo, but it won’t be our last."
- Sarah B.
"Apollo is an excellent company. I always receive great service. Alex A. was professional and friendly. He kept me informed during the process of checking my furnace and heat pump to make sure they were working properly. The company makes sure you are notified who is coming and when they are on the way. All my interactions with the company have been wonderful."
- Beverly S.



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