Carbon monoxide (CO) is an invisible, odorless, and colorless gas created by the incomplete combustion of carbon-containing fuels. The danger of CO lies in its ability to bind with hemoglobin in the blood far more readily than oxygen, effectively suffocating the body’s tissues and organs. Because this silent threat is often associated with home comfort systems, many people are concerned about air conditioning units causing this type of poisoning.
The Direct Answer: Do Air Conditioners Produce Carbon Monoxide?
The simple answer is no; air conditioning units do not produce carbon monoxide. Standard air conditioners, whether central systems or window units, operate solely on electricity to cool air through a refrigeration cycle. They cool the air by circulating refrigerants through coils, a process that does not involve fuel burning or combustion.
Carbon monoxide is exclusively a byproduct of combustion, requiring a material like natural gas, oil, wood, or propane to be burned. Since air conditioning systems do not burn fuel, they cannot generate the gas themselves. However, a cooling system can circulate CO that has leaked into the home from a different source. The risk arises from the proximity of other fuel-burning appliances or shared ventilation pathways.
Actual Sources of Carbon Monoxide in the Home Environment
Since the air conditioner is not the source, the real culprits are appliances that burn fuel within the home environment. Common household systems relying on combustion include natural gas or oil furnaces, water heaters, gas stoves, and clothes dryers. These appliances are designed to vent exhaust gases, including trace amounts of CO, safely outside the home.
A common mechanism for CO leakage involves a cracked heat exchanger within a gas furnace, which separates the combustion gases from the breathing air. Over time, the metal expands and contracts, which can lead to hairline cracks that allow CO to mix with the air being circulated into the home. Improperly maintained or vented water heaters and boilers can also produce dangerous levels of CO. Additionally, external sources like a vehicle running in an attached garage or a portable generator placed too close to a window can cause the gas to infiltrate the living space.
How Ventilation Systems Become a Pathway for CO
While the air conditioner does not create the gas, the home’s ventilation system can become a dangerous pathway for CO to spread throughout the structure. The ductwork, which handles both heating and cooling, can draw in and distribute the toxic gas that has leaked from a nearby combustion source. Cracks, gaps, or holes in the ductwork running through a basement, crawlspace, or attic can easily suck in ambient CO and circulate it to every room.
One of the most concerning pathways is backdrafting, which occurs when negative pressure in the house pulls air down the chimney or vent pipe. This can happen if high-capacity exhaust fans, such as those in kitchens or bathrooms, are running simultaneously, drawing more air out of the home than is being replaced, pulling combustion exhaust back inside. Furthermore, improper placement of outdoor air intake vents for the air conditioning system can draw in exhaust from a nearby furnace, water heater, or even a neighbor’s appliance vent. The AC fan then pressurizes the home with the contaminated air, spreading the danger quickly.
Essential Steps for Prevention and Detection
The most effective step for protection is the mandatory installation of carbon monoxide detectors in the home. Detectors should be placed on every level of the house, including the basement, and particularly near sleeping areas to ensure occupants are alerted while they are resting. Install the detectors at least 15 feet away from any fuel-burning appliances to avoid false alarms from the minor amounts of CO released during normal appliance startup.
Annual professional inspections of all fuel-burning appliances are a necessary preventative measure. A qualified technician can inspect the furnace’s heat exchanger for cracks and ensure that all appliance vents, flues, and chimneys are clear of obstructions and correctly sealed. Maintaining proper ventilation clearances around outdoor exhaust vents and ensuring the AC system’s outdoor air intake is not positioned near a potential CO source will significantly reduce the risk of accidental poisoning.