I received the following e-mail from Assistant Fire Chief Ed Murphy of the Roberts Park Fire Protection District in Justice, Illinois, who advised me of the following:

“One of my firefighters was informed of a new gypsum wallboard that is being marketed by National Gypsum. This wallboard is backed by Lexan™ substrate. This wallboard overall is 5/8 inch thick with various thicknesses of Lexan™, from 0.010 inch, 0.020 inch, 0.030 inch, and 0.080 inch. According to the manufacturer, the 0.030-inch and the 0.080-inch boards would need a Sawzall™ to penetrate the wall. This will pose a problem with breaching a wall for escape purposes and for overhaul. The manufacturer agreed that it would be very difficult to breach this type of wall. More information can be found at The product is marketed under the names of Hi-Impact brand Wallboard and Hi-Impact brand Kal-Kore Plaster Base.”

I accessed the suggested Web site and got data on National Gypsum’s Hi-Impact brand gypsum wallboard. Two issues should be investigated:

Can any technique be developed that would make it possible to break into the wallboard with existing common fire department tools?

The “estimated costs” on page 2 of the Web site include 35/8-inch, 20-gauge (steel) studs on 16-inch centers with the listed finish materials on both sides. So, presumably that is the intended installation. On page 13, the flame spread on the back surface is given as 50 or less. Gypsum wallboard is tested with an unbroken surface. In fact, a number of openings in the typical wall will admit heat to the interior of the wall. The two back surfaces will be about 31/2 inches apart.

What would be the effect of radiation and reradiation on the flame spread of the wall? The steel studs have openings for wiring, so the fire can spread throughout the wall, which is to an unknown degree resistant to fire department efforts to open it. Presumably, the area where the Lexan™ is burning would be so weakened that it could be broken in the ordinary manner. However, by the time this is done, the fire probably would have spread laterally and possibly vertically along utility paths if the wallboard resists attack. The firefighters will be playing catch-up, unable to perform the desired tactic to get ahead of the fire.

The wallboard assembly received a one-hour rating in the ASTM E 119 test developed in 1916. In a 1975 Bulletin, the Society of Fire Protection Engineers warned that codes and standards were not adequate for today’s fire loads.1

I would be interested in hearing from anyone who has encountered this material. If it is being used in your area, how do you keep track of it so firefighters will know the buildings that may present the hazards noted above? Contact me at

If you hear of a new building material that may make firefighting more difficult or dangerous, please let me know. The days of my climbing around buildings under construction with camera in hand are gone.


In the October 2003 Ol’ Professor column, I surmised that the deaths of two Memphis firefighters were caused by a fire in a combustible metal deck roof (CMDR). David White, publisher of Industrial Fire World, has informed me that the building had a built-up roof (multiple layers of roofing paper and tar) and a steel bar joist-supported metal deck roof.

I discovered the hazard of combustible metal deck roofs and how to fight them in two fires that occurred at the Marine Corps Depot of Supplies at Norfolk Virginia, in 1946 and 1948. Unfortunately, no one believed this was a problem, because such roofs were “ap-proved,” until the total loss of the General Motors Livonia (MI) transmission plant fire in 1953. The combustible metal deck roof had been set afire by a welder’s torch.

When you are told something is “ap-proved,” demand the entire report. “Ap-proved” by whom and for what? Note that UL approves nothing. It LISTS assemblies that have passed certain tests Factory Mutual Lab “approves.”2

CMDRs cannot be ventilated safely. A 54-square-foot hole was required to vent a 100- 2 20-foot test building with no contents, just the roof burning. In preplanning any steel bar joist-roofed building, determine if it has a “built-up roof.” If so, a relatively modest fire in contents that raises the temperature of the steel deck to 800°F for five minutes can set the roof on fire. Evacuate and, if possible, cool the steel decking by cutting off the gas flow from a safe location.


Another insidious hazard not often recognized by fire departments is stack effect, which was first brought to public attention by Canadian fire researchers and taught to me by Harold (Bud) Nelson, SFPE (Fellow).

You respond to a smoky fire in the lower level of a 20-story high-rise apartment house in zero degree temperatures. Would you think to send personnel, with masks in place, to the upper floors with the carbon monoxide (CO) detector? Under the same winter conditions, you respond to reports of smoke on the 20th, 19th, and 18th floors of a 20-story high-rise. Would you assume that the fire must be on the 18th floor, or would you be flexible and remember that the fire might be at a much lower level in the building?

Stack effect, the upward movement of air caused by the difference in temperature between the interior and the exterior of the building, will drive the combustion products directly to the upper floors, bypassing intermediate floors, through all vertical shafts.3

The particulate matter, which makes smoke irritating and destroys visibility, may deposit on surfaces as it rises, leaving the CO, which is colorless, odorless, and tasteless, to poison the atmosphere.

At a fire in a used magazine business in the subbasement of a New York high-rise, two firefighters, seeing little smoke in the lobby, left their SCBA in the lobby and went to the upper floors by elevator. They were found dead on an upper floor; the elevator operator had died in his car.

Have you any plan to deal with this potential problem, or will you concentrate solely on the undeniably important “putting the wet stuff on the red stuff”?4

Think outside the box. What benefit would it be to the occupants if all the efforts are devoted to extinguishing the fire while ignoring the spread of the deadly CO gas?

If this is confusing to you, consult with a local air-conditioning engineer who can explain it. On a bitter cold day, go to the top of a fairly high high-rise building and see if it is difficult to open a fire stairway door because of pressure on the stairway side.

If you live in a balmy climate, study the summer stack effect, which may make it impossible for you to establish an operating base two floors below a fire.

At Navy Norfolk, we were called to provide additional SCBA cylinders to the city for a stubborn fire in a refrigeration plant. The plant was identical to one we had preplanned on the base. I had heard of “cold smoke,” which is heavier than air, from FDNY officers who had fought fires in refrigeration plants. The fire was in a big pile of treated lumber being used room by room to rehab the plant. The chill was off in the fire room. But the temperature was about freezing because of the zero temperature in the rooms on all sides.

The firefighters were using defrost fans to remove smoke, but the smoke was simply being blown around in a circle in the corridor, which ran all around the elevator shaft, as it did in our plant. Drawing on our preplan, I suggested to the Norfolk commander that salvage covers be erected to channel the smoke to the elevator shaft. The smoke poured down the shaft like water, and the fire area was cleared. I did not learn the term “stack effect” until much later.

At Navy Norfolk, we worked very closely with the city and had equipped and trained the first salvage unit. We were very strong on salvage from any water or steam situation. It gave us great public relations and thus financial support with the brass. Fire departments should take every opportunity to demonstrate and publicize salvage work.


1. Society of Fire Protection Engineers Bulletin, 1975; Chapter 12, Trusses, Footnote 5, p 538.

2. Read and study pages 302-309 of Building Construction for the Fire Service, Third Edition (BCFS3) and “Narrow Escape” in my Ol’ Professor column, March 2001.

3. See BCFS3, pp. 481-484, for more information on stack effect.

4. See BCFS3, pp. 481-485, particularly the radical. traditional, destructive concept of fighting a lower-floor fire from the outside and opening up the inside stairways and other shafts as little as possible to the products of combustion.

FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 61-year career to the safety of firefighters in building fires. He is well known as the author of Building Construction for the Fire Service, Third Edition (National Fire Protection Association, 1992) and for his lectures and videotapes. Brannigan is an editorial advisory board member of Fire Engineering.

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