What is Positive Pressure?
Where is Positive Pressure testing required?
What hardware is affected by positive pressure requirements?
How is Positive Pressure certification being communicated?
For information about Positive Pressure
Positive pressure is a new type of fire testing for doors and hardware that is now being adopted in the U.S. market. It has been required in Europe and Asia for a number of years. The easiest way to understand the difference between the old test and the new test is to compare it to what happens in a fireplace.
In the old test, the damper on the fireplace was wide open. Therefore air entered the fireplace from the room, and smoke went up the chimney. Likewise, in the old fire test, no internal pressure was applied to the door opening. Instead, air was pulled from the non-fire side of the door into the chamber on the fire side of the door.
Now imagine that the fireplace damper is closed half way. While some of the smoke still goes up the chimney, some is also forced out of the top of the fireplace into the room. Air from the room now enters only at the bottom of the fireplace. In the positive pressure test, air is drawn into the test chamber through the clearances at the bottom of the door / frame / hardware assembly, while pressure tends to force smoke through the clearances at the top of the assembly.
In technical terms, the positive pressure test moves the neutral pressure plane from the top of the opening, where it was in the old test. to a location 40′ above the floor. In the fireplace analogy, the neutral pressure plane is the border between where air enters the fireplace and where smoke exits it. Above this plane, pressure against the opening is greater than atmospheric pressure, so the term ‘positive pressure” has been applied.
The pressure against the upper portion of the door / frame / hardware assembly will tend to force smoke and hot gases out through any small gaps between the door and frame. This creates a danger that something on the outside of the door (or the door itself) could catch fire. Part of the positive pressure test requires that any component of the door / frame / hardware assembly on the outside (non-fire side) cannot produce flames for more than 10 seconds. Hardware products that contain flammable substances such as closer fluids or potting resins can be affected by these positive pressure requirements. Some door core materials cannot only produce flames, but can also cause the entire assembly to react differently in a positive pressure test.
The positive pressure test more closely replicated what takes place in a real fire.
The International Conference of Building Officials (ICBO) changed its code, the UBC, in 1997 to require fire doors to be tested in a positive pressure environment to reflect conditions that occur in actual fires. In 2000, ICBO joined with two other major code groups, BOCA and SBCCI (Building Officials and Code Administrators, and Southern Building Code Congress International), and formed a new set of codes: the IBC (International Building Code). The IBC also requires doors to be tested to positive pressure. Currently more than 35 states (including Arizona) have adopted the IBC. Positive pressure doors will be the typical fire door required throughout the United States in the future.
In general, the only hardware affected is located in the top 1/3 of the opening, such as door closers. Weather-stripping containing intumescent materials are often required for wood door assemblies to be positive pressure certified. Existing hardware is grandfathered and need not be replaced unless there is a major renovation or replacement of the firedoor. What door constructions are affected by positive pressure requirements? All door and frame construction have been affected by this standard. All doors and frames have had to go through significant retesting to establish new listings. Some steel door constructions have had to be modified, but in general, do not require the addition of weather stripping or fire seals. Wood door constructions require the use of intumescent seals to pass the test and be listed.
A conformance statement is being added to all the labels. While these labels vary from division to division, the label should make some reference to UBC 7-2 (1997) or UL 10C. This information may be contained within the fire label or on an auxiliary label. Each brand will also provide a written positive pressure conformance statement for products manufactured before the USC 7-2 note was added to the fire label. In addition, letters of compliance should be available from all door hardware suppliers who comply with UL 10C.
Positive pressure is an improvement in protecting people and property from fire. Please call your local Authority Having Jurisdiction (AHJ) or contact Sun Door and Trim, Inc. for more information.