Heat and smoke vent
Heat and Smoke Vents are installed in buildings as an
active fire protectionmeasure. They are openings in the roof which are intended to vent the heat and smoke developed by a fire inside the building by the action of buoyancy, such that they are known as "gravity vents".
Heat and smoke vents are typically installed in buildings for the following reasons:
* Storage occupancies - The heat release rate from high piled storage commodities is expected to be very high. In such cases, it is desirable to vent the heat from the building if the temperatures in the building reaches sufficiently high levels to endanger the structural stability of the roof system. Smoke venting is desirable to increase the visibility in the interior space to facilitate manual
* Large internal volume spaces – Venting smoke from large spaces which regularly contain large numbers of people, such as malls and atria [NFPA 92B Standard for Smoke Management Systems in Malls, Atria, and Large Spaces 2005 Edition] [NFPA 101 Life Safety Code 2006 Edition A.188.8.131.52.2(6)] .
Automatic heat and smoke vents are available commercially in two general categories [ NFPA 204 Standard for Smoke and Heat Venting 2007 Edition ] :
* Mechanically opened vent, powered by springs, pneumatic actuator, or electric motor.
* Drop-out vent – constructed of plastic which shrinks in the presence of heat (i.e., drop-out panel).
Interaction with automatic fire sprinklers
The majority of guidance available for design of heat and smoke building vents installed in buildings is restricted to nonsprinklered, single-story buildings [NFPA 204 Standard for Smoke and Heat Venting 2007 Edition, 1.1 Scope] . This is partly a historical consequence of the installation of heat and smoke vents in storage buildings prior to the installation of fire sprinklers as a widespread warehousing industry practice. Subsequent to sprinklers being installed in storage buildings as a widespread practice, there has been a lack of consensus regarding the nature of the interaction of sprinklers and automatic heat and smoke vents [NFPA 204 Standard for Smoke and Heat Venting 2007 Edition, Origin and Development] . This lack of consensus continues to this day [NFPA 204 Standard for Smoke and Heat Venting 2007 Edition, F.3] .
Automatic heat and smoke vents are permitted by
model building codes in conjunction with control mode fire sprinklers, but are not permitted to be installed in with suppression mode fire sprinklers unless the vents are manually operated or have an operating mechanism with a thermal rating of not less than 360°F. [NFPA 1 Uniform Fire Code 2006 Edition, Chapter 34 General Storage, 184.108.40.206] .
Smoke exhaust ductwork
Passive fire protection
Active fire protection
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