Back Button

How to Vent an Exhaust Outside From a Combustion Engine

Bob Haring

All combustion engines -- automotive, generator, furnace and all gas-fired appliances -- need air to burn their fuel. The exhaust must be removed to keep the combustion engine working and to remove carbon monoxide from the air. About 900 Americans die each year from carbon monoxide poisoning in homes. Furnaces, gas water heaters, ranges, dryers and other appliances must be properly vented; the builder or installer normally does this. Gas generators, vehicles in garages and other combustion engines also must be vented.

All combustion engines must be properly vented outside buildings.

  1. Decide what combustion engines need venting, where they are located and where the best route for a vent would be. Appliances, such as gas ranges and dryers, normally are vented individually through the roof, although, sometimes an exterior wall will suffice. The National Fuel Gas Code offers specific rules and suggestions for such venting. It provides tables with the location, size and operation of vents. A vent that is too small or too large will not effectively remove all of the gas fumes.

  2. Use different methods for a garage, shop or other locations where automobiles or similar combustion engines will be operated. A large facility, such as a commercial automotive shop, will employ large heaters and exhaust fans. Homeowners can use such simple techniques such as a box fan in a window. Systems are also available that use vents in a wall or a garage door with outlet fans, typically placed in the ceiling or high on a wall.

  3. Using temporary or portable vent systems will often suffice with portable generators, cars and other movable combustion engines. In a home garage, where a car engine runs only during maintenance or repair, a basic reel-type venting system with a tube through the roof may work. Sometimes, a tube can be hooked directly to the automobile exhaust. A tube system also could work with a generator, although these frequently are located outside a building so venting is not required.

  4. Decide how to go through a wall or roof. At some point, any vent is going to require getting through a structure such as a wall or a roof. The National Fuel Gas Code offers suggestions on types of pipe, chimney or other outlet. A vent must not come out of an exterior wall below such extensions as eaves, parapets, balconies or decks. Exposed vent pipe should not extend outside the building as it could build up water condensation, which may freeze and block the vent.