Ventless Gas Fireplaces: What You Need to Know

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Gas and propane fireplaces provide a convenient, low-cost alternative to traditional fireplace options, but they aren’t trouble-free.

Ventless fireplaces, which don't include a flue or chimney, have been sold in the U.S. since 1980. They're powered by natural gas, propane, alcohol-based gels, or electricity. Although less expensive and easier to install than a traditional fireplace, the gas and propane options do have some risks since there's no chimney to expel their gases to the outside.

Modern ventless fireplace models are strictly regulated by federal agencies and standards groups for safe operation in your home. But the debate about their safety does continue. In fact, Massachusetts and California, as well as Canada and other countries, have outlawed gas and propane ventless fireplaces.

Here’s what you need to know about ventless options.

Types of Ventless Fireplaces

Ventless fireplaces are typically freestanding units that don't require a flue or chimney to exhaust combustion air to the outdoors, making them relatively easy to install in any room.

Those fueled by natural gas or propane can be positioned anywhere that a supply line can be installed -- usually against a wall or inside an existing masonry fireplace. The latest models also feature automatic ignition, a function that eliminates the need for an outside electrical circuit to spark the pilot light -- a handy feature should the electricity ever go out.

Gel-fueled units are even more versatile, as they're completely self-contained (not tethered to a supply line) and light with a match. Electric units need only a 120-volt outlet nearby, and a dedicated circuit isn't necessary.

What Does “Ventless” Mean?

Ventless fireplaces fueled by gas or propane rely on indoor air for combustion, and they exhaust a low level of their combustion gases into the room in which they're located. A chimney or flue isn't necessary.

The risk to your health is a long-standing and ongoing debate. Proponents suggest that any emissions are negligible, and well within indoor-air quality guidelines as set by various regulatory agencies. Essentially, these products must meet the general requirements for all combustible heating appliances established in the 2002 version of the National Fire Protection Association’s standards that require ventless fireplaces to have factory-installed carbon monoxide monitors and oxygen detection safety devices (ODS). These safety devices automatically shut off the fireplace if the carbon monoxide level in the room rises above 25 parts per million, and/or the oxygen level falls below 18% -- levels for indoor air quality suggested (but not standardized or regulated) by the U.S. Environmental Protection Agency.

Critics, however, claim that such monitors are unreliable and imprecise, allowing oxygen and carbon monoxide levels to fluctuate out of range before the units shut down, resulting in potential health hazards.

Ventless fireplaces that use gel canisters or electricity, meanwhile, are above that fray, as they don't emit anything other than a low amount of heat.

In fact, ventless fireplaces generally are just for aesthetics and supplemental space heating. Those with automatic ignition or that use gel fuel can supply a low level of room heat for short spans of time and during power outages, when electricity isn’t available.

Installation and Maintenance

Ventless fireplaces that are connected to a gas or propane line require professional installation by a gas or plumbing contractor, and shouldn't have a heating capacity that exceeds the appropriate room size recommended by the manufacturer.

Despite their relative ease of installation, and regardless of fuel source, ventless fireplaces aren't a turn-them-on-and-forget option. All units require at least annual cleaning of the log set and other exposed components, while gas and propane products should also have their oxygen and carbon monoxide monitors checked and adjusted annually for optimum performance.

Although suppliers may tout the integrity of factory-installed carbon monoxide monitors, installing a hard-wired, independent carbon monoxide monitor in the room in which the fireplace is located is a smart second tier of safety. Expect to pay $100 to $200 for an hour of an electrician’s time and the monitor.


Gas- or propane-connected ventless fireplaces usually include a factory-finished enclosure and/or mantle. With professional installation, they cost $2,000 to $6,000. Installation may not require a building permit, but check with your local building department to confirm if there are any regulations or limits on the use of a ventless fireplace.

Gel-powered ventless fireplaces generally cost less, $300 to $700, and don't require professional installation and associated costs. You'll need to assemble some of the unit, including putting the factory-supplied logs in front of the gel canisters. The fuel comes in 13-ounce canisters that cost about $3 and last about 2.5 hours each. They are sold in cases of 24 for about $80 or $110 for a dozen, 30-ounce refill bottles.

Electric fireplaces also are standalone, self-contained, and factory-finished, requiring no installation other than removing them from the box and plugging them into a wall socket. They cost about $1,000 and up, depending on the sophistication of the mantel and surround. Suppliers claim these products produce a realistic flame effect created by randomly filtered lighting, but judge for yourself at a retailer before you buy.

Choosing the Correct Size

It’s important to size a ventless fireplace for the size of its room. A large, open space, such as a great room, should handle a ventless gas/propane fireplace with a 25,000 BTU or higher output, akin to the heat output from a sealed and vented gas fireplace.

For smaller rooms, such as a bedroom or bathroom, ventless gas- or propane-fueled fireplaces can be sized down to 5,000 BTUs. For optimum control over heat output, these units can be regulated by a wall thermostat or remote control.

Gel-powered units can output up to 9,000 BTUs. Electric fireplaces, like space heaters, provide very localized output -- at most, 4,500 BTUs -- but will remain working as long as they are plugged in and switched on.

Regardless, ventless fireplaces of any kind and size are nearly 100% efficient, as very little of the heat they emit escapes the room. By contrast, an open-faced, wood-burning fireplace with a chimney may lose 85% or more of its heat output through the flue.

Related: The Warm and Cozy Home

Rich Binsacca
Rich Binsacca

Rich Binsacca has been writing about home improvement since 1987. He is the author of 12 books on home-related topics, is a contributing editor for Builder and EcoHome magazines, and has written for Remodeling, Home, and Architectural Record.