by Kurt Roeper

There's been a lot of talk about positive pressure, but the talking is over, the door and hardware industry will adapt to it as it has every other code change, and life will go on. It's time to take a reasonable look at what positive pressure entails and what its effects on the marketplace will be.

What is Positive Pressure?

Some of the controversy stems from a misunderstanding of what positive pressure really means. It is simply a term used to describe the location of the neutral pressure plane within the test furnace while the test on a fire door is being conducted. Historically, the fire door test method placed the neutral pressure plane at the top of the assembly, regardless of its overall height. Everything below the top of the door was under negative pressure, and any gasses or products of combustion were drawn into the furnace. With positive pressure, the neutral pressure plane is lowered to a standard 40 inches off the floor, so regardless of door height, the neutral pressure axis is defined from the floor upward. The effect of this change places a very gentle amount of pressure against the remaining portion of the assembly, which may push smoke, hot gasses and any potential flames out around the perimeter of the door assembly.

To envision the difference, imagine a closed door with a fan pulling the air away from the opening on the fire side. Now reverse the fan so it blows against the door. In either case, the pressure isn't that great and certainly will not affect the structural integrity of locks, latches, hinges, or frame anchors. However, with the fan blowing against the door, the products of combustion are not drawn away as they were when the fan was pulling air away from the door. If the face of a wood door is burning, the effect of positive pressure is to enhance combustion somewhat, and to drive the smoke, gasses and possibly flames through any leakage at the door perimeter. Under the previous tests, these products of combustion were carried away.

Since the fire test is designed to measure a door's ability to contain the spread of fire, the possible acceleration of combustion and breakdown of the door's ability to contain the fire could compromise a previous rating and require some redesign of non-conforming products.

Combining the Codes

The push for positive pressure began in the jurisdiction of the International Congress of Building Officials (ICBO) in the early '90s and was adopted in 1996. During this same period of time a move developed to combine the three model building codes into a single, national code, known as the International Code Council (ICC). The ICC would combine the BOCA (Building Officials and Code Administrators), SBCCI (Southern Building Code Congress International) and ICBO model codes into a single model code.

Since the existing codes of SBCCI and BOCA retained neutral pressure testing protocols, the working draft of the International Building Code was published in May, 1997, with a statement allowing the test protocol to be determined by the local authority having jurisdiction. Full resolution of this issue and implementation of the final unified code will take years.

What Needs to Be Done?

As positive pressure becomes incorporated into more and more local codes, it will primarily affect manufacturers, who will be required to meet the slightly different test criteria now included in the Uniform Building Code. Manufacturers will have to successfully complete the necessary tests and add supplemental labels to their products to be specified in localities when and where the new code is in effect.

The steel door industry can and will provide the products to meet the new standards. Steelcraft and other Steel Door Institute members have conformed to the international positive pressure test methods and protocols for many years, as part of their export business. British and Japanese Standards are among those that have recognized positive pressure as the accepted test criteria, and it has been possible to meet these standards without modification of existing steel door or frame products. The Steel Door Institute members have entered into a joint testing agreement that will subject samples of their current fire door models to positive pressure testing. This arrangement will allow the SDI member companies to continue providing the high-quality, code-compliant products for which they are known.

After many years of debate, positive pressure is a reality, and it's time for the industry to move ahead and "play the hand we're dealt." Tests, after all, only measure door performance under a standard set of conditions. The new standards will provide an interesting climate for the industry in the years ahead, a climate which is certain to contain a fair amount of confusion regarding the proper application of products. The winners will be those companies that readily adapt to change and continue to support their customers with quality products.