Carbon Monoxide can be a Silent Killer with No Warning

With December stories of the silent killer that is carbon monoxide become commonplace because poisonings that aren’t detected can kill. 

By Rebecca Martin

Carbon monoxide toxicity is often referred to as a “silent killer” in winter news articles. However, “silent killers” are often diseases which have no apparent symptoms such as high blood pressure, hypertension and diabetes. These diseases consume one from the inside without your knowledge. Carbon monoxide toxicity has very clear and substantial symptoms and a modicum of effort can prevent exposure.

Only detectors can warn of the silent killer that is Carbon monoxide poisoning.

Carbon monoxide is a silent killer that can’t be reliably detected by anything other than a properly functioning a carbon monoxide detector. Without a detector, even pets may sleep through the warning signs and die.

Although the presence of carbon monoxide is not detectable through use of our senses alone, there are many people who believe that carbon monoxide can be detected through smell. Carbon monoxide is an odorless and tasteless gas which although it can be present when there is smoke or other fumes, does not have a distinguishable smell of its own. Mercaptan is added to natural gas used to fuel homes to make it easier to detect gas leaks. Its odor has been compared to rotten eggs as sulfur is one of the components used to odorize natural gas. But while it is possible to add mercaptan to natural gas before it reaches your home, there is no method to odorize carbon monoxide to make it easier to detect. The only method of detecting dangerous levels of carbon monoxide is through the use of detectors.

Education about the Silent Killer

Education is key to understanding the dangers of carbon monoxide exposure and avoiding potential fatalities. That is why I disagree with it being referred to as a “silent killer”. The misconceptions surrounding carbon monoxide are often the conditions which lead to carbon monoxide injuries and deaths. While browsing the internet for information I encountered this statement on one home improvement website: “Remember that sulfur can cause a similar smell to carbon monoxide.” Wrong. Carbon monoxide is an odorless gas. Gas leaks can be present if one smells the rotten egg smell associated with the sulfur present in the additive, mercaptan. Again, while carbon monoxide can be present when the scent of other fumes can be detected, carbon monoxide alone cannot be detected by smell. Carbon monoxide is a by-product of combustion and can exist in the air without a fuel leak being present.

Dogs and CO detection

Can dogs detect carbon monoxide in the air? No. Carbon monoxide is an odorless gas and dogs cannot detect its presence even with their superior sense of smell. For this reason pets cannot reliably give you forewarning by smelling the CO molecule. But dogs are smaller than we are and have higher respiration rates than we do and are impacted quicker than we are. In that sense a dog may alert us to the fact that it is experiencing symptoms which may be distressing to it before we are impacted. Dogs can detect a gas leak due to the additive, mercaptan but the only warning it can give to the presence of carbon monoxide is by our understanding of common symptoms that a dog may exhibit. These symptoms include, drowsiness, weakness, incoordination, breathing problems, nausea, vomiting, and seizures. The presence of extremely red, flushed ears, gums and lips are a classic warning sign that a dog may be suffering from exposure to carbon monoxide.

I have heard countless stories of dogs (or cats) warning their owners of toxic fumes and becoming heroes. Personally, my childhood dog saved our family during a chimney fire by waking us during the night. These stories often entail the presence of smoke or gas which is detectable.

Do not ignore your pets in such situations because pets do smell unburned hydrocarbons before humans. The first level of carbon monoxide poisoning in theory involves all fuel being burned, incompletely. In such model of combustion CO will to some degree, replacing CO2 in the exhaust. But as the fuel to oxygen mixture gets even richer, as more and more fuel doesn’t get burned, then the pets may very well smell something amiss. When the Carbon monoxide levels get into the 4-6,000 ppm in the exhaust of the appliance, then even the human nose will begin to detect it. But 4-6,000 ppm concentrations in the ambient air( as opposed to the exhaust flue of an appliance) can cause almost immediate loss of consciousness.

Fresh Air May not Stop Silent Killer

Another misconception is that the presence of fresh air somehow mitigates the danger from carbon monoxide. In many of our previous blogs we have examined this misconception while exploring deaths and injuries due to carbon monoxide exposure in situations where a source of fresh air is present. From toxic levels in the rear of open boats traveling at slow speeds to toxic levels reached in garages with the door open due to back-drafting to exposure in a vehicle even with windows rolled down. The presence of fresh air does not guarantee that carbon monoxide can reach dangerous levels due to atmospheric conditions which lead to a concentration in the air which overrides the flow of oxygen into the same space.

Carbon monoxide is a silent killer due to the fact that it attaches to the hemoglobin in our blood 200-300 times faster than oxygen does. And when carbon monoxide attaches to hemoglobin it hangs on so tightly that the hemoglobin is no longer able to absorb oxygen. The body then suffers from a lack of oxygen and damage occurs.

Carbon Monoxide Tragedies

Winter carbon monoxide poisonings have been in the news this week as furnaces are turned on. In Summit County, Colorado on December 9th, a family escaped a tragic ending due to carbon monoxide poisoning produced when the furnace was turned on. Police officers had pulled over a speeding driver only to discover the person was rushing an unconscious child to the hospital. Help was dispatched to the Colorado home where another unresponsive child was discovered and five adults suffering from carbon monoxide symptoms. Seven in total were treated at the hospital. Even though the adults had ventilated the home before emergency responders arrived, toxic levels of carbon monoxide were still present. The misconception that fresh air mitigates the effects of the carbon monoxide could have been deadly in this situation. The only measure to be taken in this situation is to vacate the premises and contact emergency services.  According to Summit Fire and EMS spokesperson Steve Lipsher,

“It’s just by sheer good fortune that we didn’t have a catastrophe on our hands,” He goes on to say: “You can’t smell or taste carbon monoxide, but if it’s alerting or it’s going off in siren mode, it’s telling you get out of the residence. Call 911,”




In this instance the home was not equipped with a carbon monoxide detector. In Summit County, Colorado, Summit Fire says that carbon monoxide and smoke detectors are free to any family who cannot afford them, and they are readily available in the area for others.

One of the most urgent ways in which carbon monoxide should not be relegated into the realm of silent killers is that carbon monoxide detectors, properly placed and maintained, save lives. This simple, inexpensive preventative measure has saved countless lives. Every home with at least one fuel-burning appliance/heater should be equipped with carbon monoxide detectors. There should be a detector on every floor of the home and adjacent to every sleeping area and in the presence of an attached garage, adjacent to the attached garage. An detector is the only way to detect whether there are dangerous levels of carbon monoxide in your home.

Even in the event of a gas leak the carbon monoxide exposure can prove deadly. On December 9th a Bucks County, Pennsylvania resident lost her life as the result of carbon monoxide exposure during a gas leak apparently linked to an in-home appliance. The 51-year-old woman was found dead at the scene while her husband and adult son were hospitalized after another son arrived at the home and smelled gas. He forced entry into the home and  was able to pull the father and brother from the home. It was too late for his mother. He called emergency services who reported that the smell of gas was immediately present. A neighbor reported

“When we came and opened the windows and the doors up we stood out here talking and we started smelling the gas,”

CO and gas leaks

Even in an instance where the smell of gas was present to warn the residents of the presence of carbon monoxide, many cases of death from carbon monoxide occur while the family is sleeping. The only meaningful warning is an alert from a carbon monoxide detector close enough to a sleeping area to rouse the residents and alert them to the danger.

There are also warning signs in your home of the potential for carbon monoxide mishaps. Most of these signs warn of inadequate combustion or ventilation. Excess humidity in a room where an appliance is installed can warn of improper ventilation and also impair a detector’s ability to alert. This is a good reason to pay attention to your home’s humidifier settings as well. Sooty or other stains around an appliance might suggest a problem. The smell of something overheating or burning can be a warning sign. Backdraft from fireplaces, the lack of an upward draft or falling soot from a chimney. A fire that burns unusually slowly. With gas appliances, a warning sign might be a pilot light which blows out frequently or a yellow burner flame.

Many of the warning signs of improper ventilation or combustion can be addressed by planning for the annual inspection of furnaces and fireplaces, especially prior to the onset of the colder weather in winter. Along with maintenance planning, a good plan for the potential for power outages should be part of our winter agenda as well.

Surviving the Silent Killer is not Binary

The last misconception I want to address is the belief that when you have been involved in a carbon monoxide incident but you feel ok, then you don’t need medical attention. For every person that dies in a carbon monoxide poisoning, as many as twenty survive, with a near majority of those suffering permanent brain damage. We are discovering that even milder instances of carbon monoxide exposure can have delayed results and the potential for long range effects. Although a “full recovery” might be expected, there are problems that can arise days to weeks after an incident. The delayed sequelae of carbon monoxide can affect functions such as memory and other neurological functions. Any changes in the mental state should be brought to the attention of a medical professional.

Carbon monoxide may not be accurately labeled as one of the “silent killers” or medical conditions within ourselves which go undiagnosed but it certainly is accurately labeled the “odorless killer”.  And even in those instances where it accompanies a gas leak or other malfunction detectable by smell, the absence of adequate and appropriately placed detectors can still cost lives. In this sense, carbon monoxide safety is not an issue any of us should be silent about. Tragedies due to carbon monoxide exposure are preventable. Education about carbon monoxide facts to dispel the myths are also a part of the conversation which should not be ignored. The families impacted this week alone by carbon monoxide incidents argue clearly that silence is not a word we should associate with carbon monoxide. Carbon monoxide safety is something that should be repeated loud and often as we move forward into the winter months.

If you have fuel burning appliances/heaters in your home, you need to have carbon monoxide detectors.







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