Candles can technically cause carbon monoxide (CO) poisoning, but this scenario is extremely rare under typical household conditions. CO is a colorless, odorless gas formed as a byproduct of combustion, the burning of any carbon-based fuel. It is dangerous because it rapidly displaces oxygen in the blood, leading to oxygen deprivation in the body’s tissues. While candles produce trace amounts of this gas, the risk of poisoning is primarily associated with environmental factors that allow the gas to accumulate.
How Candles Produce Carbon Monoxide
Candle wax, whether paraffin, soy, or beeswax, is a hydrocarbon fuel composed primarily of carbon and hydrogen atoms. When a candle burns efficiently, this process is called complete combustion, where the wax reacts with an adequate supply of oxygen. This reaction produces relatively harmless byproducts: carbon dioxide and water vapor, representing the ideal, clean burn.
The problem arises during incomplete combustion, which occurs when the flame is starved of sufficient oxygen. Instead of all the carbon turning into carbon dioxide, some molecules partially oxidize, forming carbon monoxide along with soot and other particles. All burning objects produce some CO, but a well-maintained, stable candle flame in a typical room should only create minute, non-hazardous quantities.
Factors That Elevate CO Risk
The primary risk for carbon monoxide accumulation stems from environmental and usage factors that promote incomplete combustion. Poor ventilation is the most significant contributor, as a lack of fresh air limits the oxygen supply and prevents combustion byproducts from dissipating outdoors. Burning a candle in a small, sealed room for an extended period creates the conditions for CO to build up to dangerous levels.
Using multiple candles simultaneously increases the total rate of combustion and gas emission, raising the overall concentration of CO. Improper candle maintenance also plays a large role. A wick that is too long draws too much fuel, causing the flame to become excessively large and unstable. This unstable, flickering flame burns inefficiently, creating more soot and increasing CO production.
Identifying Carbon Monoxide Poisoning
Carbon monoxide is often called the “silent killer” because it is colorless, odorless, and tasteless, making it impossible to detect without technology. When inhaled, CO binds to hemoglobin, creating carboxyhemoglobin, which prevents red blood cells from carrying oxygen to the body’s vital organs. Symptoms of low-level exposure are often mistaken for the flu, including headache, dizziness, nausea, and fatigue.
Moderate exposure leads to more intense symptoms like confusion, chest pain, and loss of coordination. Since the gas can cause a person to become confused or pass out, they may not realize they are being poisoned. If you suspect CO poisoning, evacuate the area immediately to get fresh air and call emergency services.
Essential Safety Measures
The most important proactive step is ensuring adequate ventilation whenever using any combustion source. Having a window cracked open or ensuring airflow supplies fresh oxygen for complete burning and allows trace gases to disperse. For the cleanest possible burn, you should trim the wick to about one-quarter inch before lighting the candle each time.
A short wick promotes a smaller, more stable flame that is less likely to flicker and produce excess soot or CO. The ultimate safety measure for any home with a combustion source is the installation of a carbon monoxide detector. These devices should be placed near sleeping areas and on every level of the home and must be tested regularly.