Vent-Free vs Direct Vent Fireplaces

When choosing a new fireplace, you may have the choice between direct vent fireplaces and vent-free.

The Difference Between Vent-free and Direct Vent Fireplaces

A direct vent fireplace uses a coaxial pipe system to draw combustion air from the outside through the outer pipe. The inner pipe vents the exhaust through the roof or outside wall. No chimney is required although the piping can be hidden in the chimney if the fireplace is installed in one.

A vent-free fireplace operates without a chimney, or outside flues or vents. These run on propane or natural gas and most do not require electricity. They have a burner or ceramic plaque burner within the heating appliance permanently connected to the gas line.

Exhaust Gasses and Fumes

Gas combustion by-products are carbon monoxide, carbon dioxide, nitrogen dioxide and water vapor. Although modern vent-free fireplaces operate within national guidelines for these by-products, there is still a lot of concern regarding their use.

Modern vent-free systems have a unique safety pilot system that automatically shuts off the gas supply if the oxygen level in a room falls below 18 percent. 20.9 percent is the normal air level of oxygen.

Gas combustion gives off moisture as a by-product which can build up in the home if you do not have adequate ventilation or a vent to the outside. This can lead to mold and mildew problems as well as condensation.

Although no deaths have been reported due to vent-free fireplaces, if you are sensitive to fumes and airborne pollutants, or you are asthmatic, you should definitely go for a vented unit. Oxygen depletion is a real risk so never use a vent-free unit with the door shut and the room closed up.

Direct vent fireplaces are sealed so harmful gasses as well as water vapor are vented outside. This is considered by many people to be a safer alternative to vent-free systems.


Vented fireplaces are more expensive to install than vent-free models, and need finishing such as surrounds and mantel. They are efficient and a good choice for newer, more airtight homes.

A vent-free fireplace is inexpensive and have low operating costs. They produce heating during power outages as most of them don’t come with a fan. The downside to this is that the heat is not blown away from the heater so it is not a good choice for heating larger areas.

Restrictions on Use

The use of vent-free fireplaces are restricted in many areas due to the potential risks associated with their use. Before buying one of these fireplaces, check to see if they are legal in your area.


Vent free fireplaces can be installed almost anywhere, even in the center of a room, without having to be attached to the ceiling or a wall. They often have more than one see-through wall, which makes them a great feature in a room and attention getter.

One downside is that they are often more bulky than a vented unit, which can limit some applications. Vent-free units must be well maintained, this is not a hard job, but it is important.