Direct vent fireplace venting uses a coaxial pipe system (small pipe within a large pipe) and draws combustion air from the outside through the outer pipe. Some of its features are:

• An inner pipe vents the exhaust.
• Can either vent out the top or out the back, for installation versatility.
• Can vent horizontally through an outside wall, or vertically through the roof - no chimney required!
• Ideal for adding warmth & efficient heating to a cold room.
• Most are certified as "gas wall furnace" for highest efficiency.
• Zero clearance to combustibles.
• Convenient to install, space-saving depth, but requires finishing such as a mantel and surround.
• Suitable for well-insulated homes or homes with no existing chimney.
• Always have an enclosed front.
• Best choice for newer, more air tight homes.

This type of fireplace venting uses economical B-vent pipe for a chimney. Some of its features are:

• Uses room air for combustion and venting terminates above the roofline (like a furnace).
• More decorative, but lower efficiencies.
• Zero clearance to combustibles.
• Relatively easy to install; space-saving depth, but requires finishing such as a mantel and surround.
• Large traditional fireplaces in clean-face or circulating models.
• Ideal for locating anywhere in the home where B-vent can be installed.
• Less Cost than Direct Vent systems

A vent-free gas fireplace operates without a chimney, flue or vent, so you can install one just about anywhere. Modern vent-free gas fireplaces:

• Inexpensive and have low operating costs
• 99 percent energy efficient provide warmth during power outages
• Design-Certified to the latest national safety standards (ANSI Z21.11.2)
• Do not exceed 40,000 Btu/hr of heat output

Forty-five million homes worldwide and more than eight million American homes enjoy the comfort and convenience of vent-free gas fireplaces. In fact, more Americans are buying vent-free gas fireplaces than any other type of supplemental gas heating product. There are, however, some areas where these units are restricted. Check with your local building departments to see if a vent-free system can be used in your home.

How they work

Vent-free fireplaces operate using natural or propane gas. Most models do not require electricity. Natural or propane gas fuels the flame through a permanent line that is connected to a blue-flame/yellow-flame burner or ceramic plaque burner within the heating appliance.

Inside air quality

The primary gas combustion byproducts that can affect indoor air quality are carbon monoxide, carbon dioxide, nitrogen dioxide, oxygen, and water vapor (humidity). Today's vent-free fireplaces operate well within national standards and recommendations concerning these five byproducts. The American Gas Association research division (www.aga.org) confirms these low emission levels.

Oxygen Detection Safety-Pilot

Since 1980 vent-free-gas-heating appliances have been equipped with a unique safety pilot system called an “oxygen detection safety pilot,” or ODS. The ODS is the technological innovation that revolutionized the safety of vent-free gas heating appliances by automatically shutting off the gas supply in the rare event that the oxygen level in the room falls to 18 percent, where carbon monoxide production can drastically increase (~20.9 percent is considered a normal oxygen level).
Previously, questions remained about the long-term effect of vent-free gas fireplace emissions on indoor air quality. In 1995 the Vent-Free Gas Products Alliance of the Gas Appliance Manufacturers Association (Vent-free gas product alliance) commissioned a study on indoor air quality as it relates to vent-free gas heating products in the home. The results proved that vent-free gas heating products meet or exceed the most current and applicable nationally recognized standards and guidelines for inside air quality.