Ventless fireplaces (duct-free fireplaces and room-venting fireplaces), are a type of residential gas-heating device.  Ventless fireplaces are preferred because they burn at nearly 100% efficiency, release far less harmful gasses than most other portable heating alternatives, and their installation is restricted little by architectural constraints. But did you know they could cause an asthma flare up?

When homeowners ask me how to make their homes friendlier to those with lung disease, I do not recommend installing a ventless fireplace. Part of the reason is because the installation of ventless fireplaces involves making a technical judgement about the “tightness” or insulation of a home or room. If the home is very well insulated, manufacturers require additional venting connections to outdoor spaces. This begs the question, “why have supplemental heating if you have to bring in exterior (cold) air?”

These units usually burn natural gas. The byproducts of natural gas are carbon dioxide and water vapor.Carbon dioxide is an odorless, invisible and potentially lethal poisonous gas. Any time these gasses are burned something must be done with their byproducts.  In a traditional heating unit these byproducts are dispelled out of a flu or vent.

Why then are these gasses not vented in “ventless” units? First, they burn such a small amount of gas that any buildup of Co2 will usually “leak” naturally out of a home.  Second, all units have a safety device known as an Oxygen Depletion Sensing device (ODS) that shuts off the unit when carbon dioxide levels get too high.

Asthma sufferers are sensitive to humidity, and low levels of carbon dioxide, even when it is nowhere near a poisonous level.  Adding one of these units may exacerbate ones asthma, and the potential asthma of any visitor.  This is important to think about since these units are often used heavily during the holidays when families get together

If you’re looking to install a fireplace into your home, there are many types to consider. Make sure to research your options and if they will have any impact on your health.