Are Vent Free Gas Heaters Safe

Many people consider using “Vent-Free” gas logs, inserts, or other heating devices to supplement, or in some cases, supply a main source of heat. I sometimes inspect them during my Home Inspections in WV. The question always comes up-“are they safe?”  Let’s put a little light on the subject.

First of all, there is no such thing as “vent free”. These devices are actually “vent less”, which technically means they have no external vent. Ventilation is provided from within the space that is being heated. Virtually all of the heat from the device is dispersed back into that space, which, as claimed by most manufacturers, makes them 99% efficient. So why wouldn’t they be safe? Let’s consider how they work.

Perfect combustion will produce carbon dioxide, and water. These devices accomplish near perfect combustion, so as long as there is adequate ventilation, and they are installed properly, there is enough fresh air flow, or exchange of fresh air to operate smoothly. However, many homes today are built close to “air tight”, to minimize energy loss. If the home (or room) is too tight, and there is not adequate air flow, then the oxygen (fresh air) could be displaced by the carbon dioxide, which could produce deadly carbon monoxide gases. Not good. But the good news is these devices are required to be equipped with an oxygen depletion sensor (ODS), which shuts the unit off if the oxygen in the room drops to unsafe levels, about 18%. So even if the unit is not installed correctly, or there is inadequate fresh air, it is unlikey the home or room would reach toxic levels of carbon monoxide.

So, the short answer to the question is “yes, they can be safe, but like any tool, they can be dangerous if used improperly, installed incorrectly, or left unattended”. Nothing will replace common sense and safe practice. Always install carbon monoxide detectors in areas where combustible gases are used. And be sure to keep smoke alarms in working order.

So cozy up, get warm. These products, when installed and maintained correctly are a safe and efficient means to economically heat a space, where needed, when needed. But remember-ventilation is everything-even for a “vent-free” device.