What Does Vent Hood Mean?
A vent hood is a type of exhaust hood used to remove hazards or unwanted contaminants (i.e., heat, fumes, and dusts) from an area. Vent hoods are positioned directly above the area in which the unwanted emissions will be released, such as above an oven that is used to boil a liquid requiring steam venting.
The defining characteristic of a vent hood is that it contains a vent to move contaminants outside of the environment in which the contaminant is being generated.
Safeopedia Explains Vent Hood
In occupational settings, vent hoods are commonly used in situations where chemicals are being used in a manner that may emit a harmful fume. A vent hood may include a fan capable of accelerating the movement of fumes upward and through the ventilation system, or it may remove fumes through passive airflow. Vent hoods do not include hoods that remove fumes and other contaminants by moving air through a filtration system, such as a charcoal filter.
There are two main types of devices that are commonly referred to as “vent hoods.” The first are kitchen hoods, which are commonly used over household stoves and ranges. These hoods are typically held high toward the ceiling, as the individual using the stove is not expected to need protection from contact with the substances being used on the stove.
The second type of vent hood is a fume hood, which is more commonly used in occupational contexts in which hazardous fume-emitting substances are used. Fume hoods typically extend much lower over the working area than kitchen hoods do, as they are used to prevent workers and their environment from being contaminated with far more hazardous or otherwise problematic substances than kitchen hoods are meant to deal with. The portion of the hood that extends downward is referred to as the enclosure, the front of which is called the sash.
The simplest type of fume hood, a canopy hood, is similar to a kitchen hood. Like a kitchen hood, it is designed to remove non-hazardous substances and lacks the low-hanging enclosure that other fume hoods use to prevent contamination of the work environment. More robust laboratory-quality fume hoods typically use more complex ventilation systems, referred to as constant air volume (CAV) and variable air volume (VAV) ventilation systems.
In the United States, the correct use of vent hoods for laboratory work is legally prescribed by OSHA 1910.45, which provides a set of laboratory design standards that includes necessary specifications for the use of fume hoods. ANSI, the NFPA, and a number of other consensus standards organizations also provide recognized standards for the use of ventilation hoods in occupational contexts.