|What is Smoke and Draft Control?
Most people are aware that in large building fires that have resulted in
deaths, smoke inhalation is by far the largest actual cause of death.
Modern building codes, therefore, include a number of requirements designed
to prevent the spread of smoke when a fire occurs to areas remote from the
fire origin. In order to accomplish this any penetrations through walls,
floors or ceilings that are part of the containment system need to be well
sealed in a manner that will not be readily compromised by the occurrence
of a fire.
Since many fire barriers must now also be effective barriers to the migration
of smoke, it is important that doors installed in these walls also be effective
smoke barriers. The recent code revisions have required specific tests to verify
that rated assemblies will provide a specified level of protection against smoke
migration. In most cases these barriers also serve a second function by reducing
the flow of air between areas of the building (draft control) which can help in
slowing the fire growth and spread by restricting the supply of fresh oxygen.
Leakage rate tests are performed to verify that the door assembly, when closed and
latched, allows no more than a prescribed amount of leakage at a specified pressure
difference. These tests are generally run both at ambient and elevated temperatures,
in both directions (i.e. positive and negative pressure relative to the door swing
direction) and at several pressure differences. In general, some sort of gasketing
must be applied to the door/frame edge to meet these smoke and draft control
In addition, to the air leakage tests, smoke and draft control assemblies must also
comply with the positive pressure fire test requirements to ensure that the system
used to provide the required level of sealing does not itself compromise the fire
resistance of the barrier. This is required on virtually all smoke and draft control
assemblies per applicable building codes.
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