Volume 2 Issue 2 Summer 2001
a o p e
Positive Pressure Testing Nears Resolution
by Alan J. Campbell
Despite some continuing controversy over the exact nature of changes in building codes, experts predict that positive-pressure fire testing for doors will replace neutral testing methods in most jurisdictions within the next two years. The years-long wrangling over the issue appears headed for a resolution.
The biggest issue still facing the door industry centers on the exact nature of the new code language. Also causing consternation are how that language will affect door products and how specifiers will be able to determine what products meet the new codes.
The problem is compounded by the nature of codes in this nation, where adjacent jurisdictions can often be adhering to different standards. Thus far, no agreement has been reached between different code writers over such issues as proper testing methods, certification and labeling of compliant units and installation techniques. These issues must be resolved before the puzzle is sorted out completely.
|“There still is some question as to whether the
new testing methods
will require manufacturers to have all of their doors and windows retested
under the new criteria and whether existing designs would meet the new standards.”
Understanding the Controversy
To understand the debate, we must first look at the historical aspects of positive-pressure testing. Fire protection experts have been clamoring for a change to positive testing for at least ten years. The issue came to light primarily through the efforts of John G. (Gus) Degenkolb. While chairman of the National Fire Protection Association’s NFPA80, Standard for Fire Doors and Fire Windows, Degenkolb raised the point that positive pressure replicates what happens in a real building fire more closely than the traditional U.S. testing under negative or neutral pressure. To bolster his argument, Degenkolb pointed out that most international codes use positive tests.
During fire tests, pressures develop in a furnace. Positive pressure forces air out of the furnace. Traditionally, with so-called “neutral” pressure testing, negative pressure sucks air into the furnace. The experts argue that this cooler outside air lowers the temperature inside the furnace in areas where the air is coming through cracks and openings. It also can cause faster burning due to an increase in the supply of oxygen.
During positive pressure testing, the test method requires that a neutral pressure plane be established to create a positive pressure at the top of door or window assemblies undergoing the test. The result is to minimize the impact of potential negative pressure points to limit the pressure differences.
Proponents of positive testing have also argued that hot furnace gases are forced out through cracks or openings in the assembly, which could cause failure. In wood-edged doors, for example, fire could burn along the edges until reaching the outside face. Similarly, wood frames may transfer fire to the face, and gases from wood cores can ignite and cause the unexposed face to ignite.
United Building Code
Also covered in the United Building Code (UBC) are smoke and draft control assemblies, wherein testing requires measurement of air leakage through the assembly at both room temperatures and temperatures of 400 degrees F.
The first body to adopt positive pressure testing as part of its code was the UBC in 1997. The debate over positive testing, which had raged for nearly a decade, came to a head with the publishing of that code.
Opponents argued against the need for a change in testing methods. The prior testing method had worked, so why change it? They also argued that if the change were made, it would be necessary to drop a provision requiring a hose stream test, wherein a stream from a fire hose was directed at the door immediately after the fire-endurance test was completed. Naysayers suggested that the combination of positive pressure testing and the hose stream test would make the new test method far too difficult to pass.
No Signs of Cooling
Arguments continue to rage, even while positive testing draws near. There is still some question as to whether the new testing methods will require manufacturers to have all of their doors and windows retested under the new criteria and whether existing designs would meet the new standards. Also unclear is how soon products conforming under the new testing methods would need to be ready for the marketplace and how interested parties will be able to know which products comply and which do not.
At the Window and Door Manufacturers Association, we are well aware of the debate. To help sort out what is going on in the code community, we recently published the Technical Bulletin: Positive Pressure Fire Doors. It is available free on our website at www.wdma.com. Follow the menus to information, literature and tech bulletin. We hope that designers, product specifiers, code officials and our manufacturers will find it useful in understanding the issue of positive pressure testing. Questions concerning the issue can also be funneled through our offices on this and other issues facing the window and door industry.
Alan J. Campbell, CAE, serves as president of the Window and Door Manufacturers Association, based in Des Plaines, Ill.
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