FAQ

Any licensed distributor/machiner authorized to label doors and/or frames by suppliers listed in this directory is eligible to label those doors and/or frames for “Positive Pressure”.

First, you will need to obtain updated specifications that include procedures for products complying with UBC-7-2-97/UL-10C. These are available through your listing agency, with authorization by your supplier(s).

Second, you will need to obtain labels that indicate UBC-7-2-97/UL-10C compliance. These can be “half-tab” supplemental labels or full labels custom printed for this purpose.

Third, you will need to obtain an updated “Authorization to Mark” form signed by your listing agency representative.

When a fire starts in a closed room, heat is generated causing smoke and gases to rapidly expand. This creates a higher or “positive” pressure in the fire room than in the surrounding area. In addition, the hot gases rise due to their lower density and greater bouyancy.

Full scale room fire experiments have shown that these forces generally result in a sort of equilibrium once the fire is fully developed where negative pressure in the room relative to the outside exists in the lower part of the room and positive pressure exists in the higher levels. The area where these two zones meet is known as the “Neutral Pressure Plane”. This plane is generally horizontal and the pressure in the room becomes increasingly more positive the higher it is measured above this plain and more negative with increasing distance below the neutral pressure plane.

In the case of fire door tests, there has been a substantial change over the course of the last several years in recognition of the need to make tests more closely simulate the type of pressure profile that is felt to be a good representation of the way many fires actually behave. It has been recognized that the level of pressure difference is less critical than the fact that it exists and tends to drive a flow of hot gases and flame out of the fire area. Thus most US fire test standards for fire doors and windows now include a specific requirement for location of the “neutral pressure plane” relative to the assembly height. This level is fixed at 40″ above the sill for door assemblies and 2/3 down from the top of window assemblies. These locations are consistent with observation during room fire experiments and also correspond to the levels already specified in most international fire test standards.

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 requirements.

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.