by | Loss Control, Safety |

All is quiet as a family sleeps. Little do they know that a silent stalker is infiltrating their home. Initially, there is no warning except for the dog stirring, yet they go back to sleep, too tired to investigate. The ending could be tragic or it could simply be an event. Which will it be?

That silent stalker is highly poisonous gas that is nearly impossible for the human senses to detect. At least 170 people die every year from non-automotive carbon monoxide (CO) poisonings. If I am a parent, landlord, hotel owner or even a business owner, I would be smart to become aware of potential causes of carbon monoxide poisoning and install working carbon monoxide detectors.

CO alarms should sound at CO levels of: 30 parts per million (ppm) for 30 days, 70 ppm for 20-240 minutes 150ppm for 10-50 minutes, and 400ppm for 4-15 minutes (UL2034). One can see as the CO ppm level increases, the time till alarm drops quickly. OSHA requires the atmosphere for employees to be less than 50ppm for an eight hour average and not to exceed 100ppm.What is CO? CO is a colorless, odorless gas that is produced from the incomplete combustion of fuels like coal, wood or charcoal. CO has a great affinity for our hemoglobin, in fact at least 210 times greater than oxygen. What does this mean? Once we are exposed to high or long durations of CO, we are in danger of injury and fatalities since the CO binds to the hemoglobin and is hard to be displaced by oxygen in our lungs. High concentrations in our blood will require medical intervention.

The initial symptoms2 of low to moderate CO poisoning are similar to the flu (but without the fever):High level CO poisoning results in progressively more severe symptoms2, including:
  • Headache
  • Fatigue
  • Shortness of breath
  • Nausea
  • Dizziness
  • Mental confusion
  • Vomiting
  • Loss of muscular coordination
  • Loss of consciousness
  • Death

What causes CO to build up in a home, apartment or business? Generally the vent is blocked by snow, debris or possibly a rodent’s nest. Newer heating units are generally condensing boilers and furnaces. The condensing units are exceptionally efficient, so much that the flue gases are generally around 120°-140°F on a normal day. On a cold day, one can see the exit gas temperature is 79°F on an 18°F day. See image to the right. The low exit vent temperature does not melt snow away during heavy snow storms from the vent opening. If vented through a chimney, the cooler gases may not have enough heat on the coldest of days to overcome the thermal requirements to escape the building. Additionally, running a generator in or near the garage can also lead to CO build up. Operating certain space heaters without adequate ventilation or in small areas can increase the CO levels.

Some actions to consider:

  1. Be sure to check the vent for your fuel burning appliance before using to ensure snow has not blocked the vent.
  2. Install CO alarms near bedrooms and at least 1 on each level and in the area the boiler/furnace/gas fireplace are located.
  3. Invest the $35 and have a CO alarm installed in your business if you have oil or gas fired heating appliances.
  4. Know your state laws. Most states have CO requirements for hotels, apartments and homes.
  5. Train your family, employees and others in regards to the dangers & symptoms of CO and how CO alarms operate.
  6. Call the fire department if you suspect dangerous levels of CO in your home/business or if the CO alarms are set off.
  7. For more information visit the U.S. Consumer Product Safety Commission’s site on CO Safety.

Luckily, the story noted at the beginning of this post had a good ending. The family was awoken by a CO alarm, called the Fire Department and ventilated the house at 2AM. Snow had blocked the boiler’s vent causing the home to have levels of CO between 200-300ppm, dangerous and potentially lethal levels. Don’t be a statistic, check your boiler or furnace’s vent, run your generator outside and away from your home, and install a CO alarm on each level of the building or home.


Acadia Insurance is pleased to share this material with its customers.  Please note, however, that nothing in this document should be construed as legal advice or the provision of professional consulting services.  This material is for general informational purposes only, and while reasonable care has been utilized in compiling this information, no warranty or representation is made as to accuracy or completeness.  Distribution of this information does not constitute an assumption by us of your obligations to provide a safe workplace. Maintaining a safe workplace in accordance with all laws is your responsibility. We make no representation or warranty that our activities or recommendations will place you in compliance with law, relieve you of potential liability or ensure your premises or operations are safe. We exercise no control over your premises or operations and have no responsibility or authority to implement loss prevention practices or procedures.

  1. Ganong WF. Review of Medical Physiology. Norwalk Ct: Appleton & Lange, 1995
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