May, 2009
Inspection News and Views from the American Society of Home Inspectors

The Word: Vent


With gratitude and an apology to Stephen Colbert, we continue an occasional column about words we use as home inspectors. We discuss words that are sometimes misused or misspelled. This column won’t be as funny as the Colbert Report, but The Word hopes you will find it informative and maybe a little entertaining.

The Word’s word today is vent. The Word recommends that you restrict use of the word vent to two components. One component is plumbing pipes that let air into drain and waste pipes to protect traps from siphoning. The word vent also describes the process of providing air to the drain and waste pipes. The second component (usually metal or plastic) conducts combustion gasses from gas and liquid-fuel-burning appliances to the outdoors. The word vent also describes the process of conducting combustion gasses from appliances to the outdoors. The Word recommends this not because other uses of the word vent are necessarily wrong, but because they can be confusing.

A common, but confusing, use of the word vent is as an abbreviation for the word ventilation, as in a crawl space vent or a dryer vent. Crawl spaces and attics are ventilated, not vented, and The Word recommends using the term ventilation opening to describe crawl space and attic openings. As an example of the potential confusion between the words vent and ventilation: Does the term attic vent mean a furnace or a similar vent in the attic or does it mean an attic ventilation opening?


Another common, but confusing, use of the word vent involves clothes dryers, kitchen range hoods and fans used in bathrooms and laundry rooms. These components are exhausted, not vented, and The Word recommends using terms such as clothes dryer exhaust duct, kitchen exhaust hood and bathroom exhaust fan. As an example of the potential confusion between the words vent and exhaust: Does the term laundry vent mean clothes dryer exhaust duct or does it mean laundry exhaust fan duct?

A word that is related to vent and is often used in place of vent is the word flue. Flue and vent describe similar components, but the words are not synonyms, so you should not use them interchangeably. For clarity and consistency, The Word recommends that you use the word vent when describing gas- and liquid-fuel-burning appliances and that you use the word flue when describing solid-fuel-burning appliances and chimneys. The terms flue vent and vent flue are redundant and you should not use them. The Word’s recommended uses are consistent with the International Residential Code (IRC), although even the IRC is not completely consistent.

A less common term that is related to the word vent is the term vent connector. If the vent is directly above the appliance, then the vent begins at the appliance flue collar or draft hood. If the vent is not directly above the appliance, then a vent connector is installed between the appliance and the vent (or the flue if a chimney is used instead of a vent).

The difference between a vent and a vent connector is important because the installation and sizing rules may be different. Vent connectors may not be installed in an enclosed location (such as within an enclosed wall), and they may not pass through walls, floors, ceilings and roofs. This restriction does not apply to vent connectors made from listed vent components, such as a Type B vent or a Type L vent. The rules for vent connector sizing are complex and well beyond the scope of this column. Refer to IRC Chapter 24 for gas vent connector rules and to IRC Chapter 18 for liquid- and solid-fuel vent connector rules.

Applause, and cut to a commercial for Simpson (they make vents, too, under the brand Dura-Vent).

Memo to the Plumbing and HVAC Gods and other authorities: The Word does not reside on Mt. Olympus and welcomes other viewpoints. Send your lightning bolts or e-mails to Please cite the authoritative references that support your position. Note that all references are not considered authoritative. Unless you are fortunate enough to have a Resident Librarian, as The Word does, consult your local reference librarian. We will continue this discussion, if warranted.