Carbon monoxide (CO) is a colorless, odorless, and tasteless gas produced by the incomplete combustion of carbon-containing fuels. This gas is often referred to as the “silent killer” because it offers no sensory warning to a person being exposed. CO is toxic and can lead to poisoning, severe tissue damage, and even death by preventing the body from using oxygen correctly.
The Odorless Threat
The primary danger of carbon monoxide lies in its chemical properties, allowing it to bypass the body’s natural defense mechanisms of sight, smell, and taste. Because it is non-irritating, a person can breathe in toxic concentrations without coughing or noticing any physical sensation until poisoning symptoms begin. This lack of sensory detection makes CO particularly hazardous while a person is sleeping, as exposure can become fatal before symptoms are recognized.
Carbon monoxide poisoning occurs when the gas enters the bloodstream and binds to hemoglobin, the protein in red blood cells responsible for carrying oxygen. CO has an affinity for hemoglobin that is approximately 200 to 270 times greater than that of oxygen, quickly displacing oxygen molecules. This forms carboxyhemoglobin, which significantly reduces the blood’s ability to deliver oxygen to vital organs and tissues. The resulting cellular hypoxia affects the organs with the highest oxygen demand first, namely the brain and the heart.
Common Sources of Carbon Monoxide
Carbon monoxide is a byproduct of any process where carbon-based fuels are burned without enough oxygen for complete combustion. The most frequent sources of CO within a home are fuel-burning appliances such as furnaces, gas water heaters, and gas stoves. Blocked chimneys or vents can prevent the exhaust from escaping, causing the gas to back up into the living space. Outdoor equipment used improperly indoors also presents a significant risk, including portable generators, charcoal grills, and gas-powered lawn equipment. Running a car or other gasoline-powered vehicle in an attached garage can allow dangerous levels of CO to seep into the house.
Recognizing Early Warning Signs
Mild Symptoms
Since the gas is undetectable, the only way to recognize a problem without an alarm is through the physical symptoms of poisoning. Early symptoms of carbon monoxide exposure are often vague and can easily be mistaken for a common illness like the flu or a headache. These mild signs include a dull, frontal headache, general weakness, dizziness, and mild nausea or vomiting.
Moderate and Severe Poisoning
As exposure increases, symptoms progress to a moderate stage, severely impacting the central nervous system. A person may experience confusion, blurred vision, loss of muscle control, and vertigo. At this stage, judgment becomes impaired, making it difficult for the affected person to recognize the danger or take appropriate action.
Severe poisoning occurs with higher concentrations or longer exposure times, requiring immediate emergency intervention. Signs include shortness of breath, chest pain, seizures, loss of consciousness, and potentially permanent brain damage or death. If these symptoms appear, especially when multiple people feel ill simultaneously, the immediate action is to move everyone to fresh air and call emergency services.
Essential Home Safety and Detection
Because human senses cannot detect carbon monoxide, a specialized mechanical detector is the only reliable way to monitor the air. Carbon monoxide alarms should be certified to industry standards, such as UL 2034, ensuring the device alerts occupants before CO reaches dangerous levels. These alarms sound an alert based on the concentration and duration of the exposure, with faster alarms for higher concentrations.
Proper placement is necessary for an alarm’s effectiveness, and it is recommended to install a CO alarm on every level of the home, including the basement. The most important locations are near or within ten feet of each separate sleeping area, where the alarm can wake occupants. Alarms should be tested regularly, typically once a month, and the entire unit needs to be replaced every five to seven years, as the sensor degrades over time.