The Pros and Cons of a Ventless Fireplace

Mariel Loveland
Written by Mariel Loveland
Updated October 21, 2021
Modern luxury home with roaring fire
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Ventless fireplaces have ignited a debate among homeowners who worry about the risk of carbon monoxide exposure

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Ventless fireplaces are an easy and affordable way to fill your home with warmth—but are they safe? Though the CDC doesn’t specifically track carbon monoxide exposure from ventless fireplaces, it’s a concern for some homeowners. Learn the pros and cons before you make your decision.

What Is a Ventless Fireplace?

Ventless fireplaces, also known as unvented or vent-free fireplaces, are a type of fireplace that uses natural gas or propane in a gas burner to create a flame that runs around gaps in artificial logs or coals. In other words: it looks like a conventional fireplace, but you’re not burning wood. 

The main draw is that there’s no smoke, so you don’t need a chimney or flue, but that’s also why some wonder if ventless fireplaces are safe. Without a chimney, carbon monoxide and other fumes are vented right into the room (albeit in small amounts, as long as everything is working properly).

The Advantages of Ventless Fireplaces

Ventless fireplaces are a popular option for homeowners who love the look of a fireplace, but would struggle to put a traditional fireplace in their home.  When it’s between a ventless fireplace or no fireplace at all, does ventless always win out? Here are the advantages. 

There’s No Need for a Chimney

First off, ventless gas fireplaces are a popular choice because not everyone has a chimney (or a working chimney). Even if you do, you may not want to deal with chimney maintenance, which includes the threat of squirrels infiltrating your space and clearing out fall leaves. Ventless fireplaces are typically serviced just once a year.

Ventless Fireplaces Are Inexpensive

Ventless fireplaces are more affordable than a conventional fireplace. A custom ventless gas fireplace can cost between $2,500 and $4,000, whereas a vented fireplace can cost between $5,000 and $6,000

Ventless Fireplaces Are More Efficient

Ventless fireplace in modern bedroom
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Vented fireplaces are designed to be more efficient than wood-burning fireplaces. According to the Hearth, Patio, and Barbecue Association (HPBA), they boast efficiency rates of 99%—a stark contrast to the 70% to 85% efficiency of vented units. Plus, you don’t have to worry about storing enough wood.

The Disadvantages of Ventless Fireplaces

For some homeowners, ventless fireplaces are more trouble than they’re worth. This type of fireplace must be meticulously maintained, and there are some concerns about safety. 

Without Proper Maintenance, Ventless Fireplaces Pose a Risk

Are ventless fireplaces safe to use? Though vent-free fireplaces are considered “smokeless,” burning gas still creates byproducts that you don’t necessarily want to inhale in large quantities (think: carbon dioxide, carbon monoxide, sulfur dioxide, etc.). 

The National Association of Certified Home Inspectors (NACHI) warns that ventless fireplaces actively vent unburned combustion products into your home—but that’s not necessarily unsafe for healthy individuals.

Most ventless gas fireplaces have an oxygen-depletion sensor (ODS) that shuts down the fireplace if oxygen levels in your home become dangerously low. Unfortunately, sensors can get clogged with dust and other particles if they’re not properly maintained. 

To help ensure safety:

  • Have your fireplace inspected annually for things like gas leaks, high gas-input rates, clogs, and other safety hazards

  • Make sure your fireplace sensor is free of dust and other particles

  • Check that the logs are placed correctly per the manufacturer’s instructions

If your logs aren’t in the right place, it can create black soot, and the logs will produce carbon monoxide. There should be a diagram in the instructions, but it’s probably wise to install a carbon monoxide detector near your fireplace, anyway.

Ventless Gas Fireplaces Can Affect Those Vulnerable to Carbon Monoxide

No matter how you swing it, even if your ventless gas fireplace is working correctly, it will emit small amounts of carbon monoxide. 

These levels aren’t typically harmful for healthy individuals, but it can be a problem for those who are vulnerable, including:

  • Children

  • Pregnant people

  • Older adults

  • Small pets

  • People with cardiovascular problems

  • People with asthma or severe allergies

  • People with other pre-existing health conditions

As the NACHI points out, this is why vent-free fireplaces have been met with safety complaints from numerous watchdog groups, including the Environmental Protection Agency (EPA), the Centers for Disease Control (CDC), the Mayo Clinic, and the American Lung Association. 

“Generally, we don’t recommend combustion products for people with health problems,” says Angela Tin, the American Lung Association’s vice president of environmental health. “But for healthy people, if the carbon monoxide sensors are working properly, they would seem to be fine.”

Ventless Fireplaces Cause Humidity

Ventless fireplaces emit water vapor, which seems a lot less scary than something like carbon monoxide, but it can still cause a problem in your home. High humidity perpetuates the growth of mold and mildew in your home, which can trigger health problems—especially if someone in your family is asthmatic. Humidity can also peel your wallpaper and cause structural damage.

There’s a hearty debate about whether or not ventless fireplaces actually cause enough humidity to pose a problem. It seems to depend on the size and ventilation of the room and how often you use your fireplace. You may need to invest in a dehumidifier or crack a window to help water vapor escape.

Vent-Free Fireplaces Are Banned in Some States

You may want a ventless fireplace, but that doesn’t mean you can have a ventless fireplace. This type of fireplace is closely regulated. In some states, like California, they’re outright banned. In other states, like Massachusetts, you need a permit and can’t put them in a bedroom or bathroom. 

At the end of the day, if you do want a ventless fireplace, most risks can be mitigated if your unit is installed and maintained by a licensed fireplace company. Remember to never run a ventless fireplace while you’re sleeping or for more than two hours at a time. It’s also probably a good idea to have carbon monoxide detectors throughout your home to help keep you and your family safe.

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