Do Modern Gas Space Heaters Really Need to Be Vented?

Carbon Monoxide

• Carbon monoxide is one of the many concerns associated with unvented space heaters. It is sometimes claimed that no dangerous levels of carbon monoxide are measured in homes using ventless heaters. However, what isn't always mentioned is that these heaters can generate low levels of carbon monoxide. While acute carbon monoxide poisoning isn't a primary concern with a modern unvented heater, long-term, low-level exposure to the gas can also have health consequences that could be avoided simply by using a properly vented heater.

Water Vapor

• Heaters with a vent expel water vapor to the outdoors in addition to expelling all the other chemicals and pollutants that are produced during the combustion process. This means that on an unvented heater, water vapor collects inside the house. This is undesirable because the additional humidity contributes to the growth of mold in the home. If you insist on using an unvented heater, make sure that your space has good ventilation and that you use a dehumidifier to prevent mold and moisture buildup.

Other Pollutants and Safety Features

• Running an unvented heater puts other pollutants into the air, such as nitrous oxide and sulfur dioxide. Modern unvented heaters have safety features such as oxygen sensors that are supposed to shut the units down when oxygen levels in a room get too low. The fact that this is a concern, and that your safety could potentially rely on a single safety feature, should be a red flag for anyone considering this type of heater. Anyone with weak lungs or a weakened constitution could experience breathing and lung problems when using these types of heaters.

Regulations

• Another factor you must consider is the law in your state regarding the use of unvented gas heaters. In a handful of states, natural gas heaters that are not vented are prohibited. You should check local regulations regarding the use of these heaters before you use one in the house. Review the restrictions in your home insurance policy as well. Some carriers may not offer you coverage for accidents related to unvented gas heaters.