VENTILATION PROBLEMS
BY BOB PRESSLER
On arrival, you find heavy smoke issuing from a two-story, multiple-occupancy commercial building of ordinary construction. The smoke seems to be pushing from every part of the building. Roll-down security gates hamper operations as you try to determine which occupancy is actually the one burning. The truck company splits into two teams. The first team, along with the officer, will operate at street level to remove the padlocks on the gates of all the stores, starting with the one that appears to be pushing the heaviest smoke. The second team will ascend to the roof position to try to provide vertical ventilation as well as to inform the incident commander of conditions in the rear of the building.
As the smoke condition worsens, the roof team (two firefighters) proceeds from the front parapet out onto the roof surface, making sweeping motions with their tools in the near-zero visibility. The team looks for roof features such as bulkheads and scuttles to aid in vertical ventilation. Sweeping with the hand tools also helps them avoid stepping into any holes in the roof or walking off the roof.
The roof team makes it to the rear wall without encountering any roof structures. A quick look over the back shows no visible fire–only a heavy smoke condition and windows sealed with masonry block. One member relays this information to the IC via portable radio. Since there are no natural openings for the roof team to open, the decision is made to cut the roof with a power saw. As the spinning blade makes contact with the roof surface, a piercing screech accompanied by a shower of sparks startles the roof team. Moving to a new position and trying again produces the same results. They notify the IC that it appears the fire building has a steel roof and ventilation will be delayed.
STEEL PLATING
In crime-ridden areas of the country, many store owners, looking to reduce the risk of break-ins via the roof, have installed steel plating on top of the existing roof. To do this, first all natural openings (skylights, scuttles, etc.) are removed and the openings are covered over. The steel–usually either 18 inch or 116 inch thick–then is lowered into position. Depending on the installation, the joints may be welded. After all the plates are in place, the steel is covered with roofing material to protect and seal the roof surface.
The addition of this plating adds between eight and 10 pounds per square foot to the dead load of the building. The whole process of adding the steel is time-consuming and relatively expensive–thus such plating usually is not found on smaller stores that do not do high-volume business (with the exception of jewelry and liquor stores). In wooden structures, steel plating also may be used to cover walls and ceilings to prevent burglars from entering through them.
Other methods of covering roofs include using a grid of two-inch steel straps (usually with individual openings in the grid of under one square foot) and using chain-link fence and tarring over it.
When operating units encounter steel plating, they immediately should notify the IC and all other personnel on the fireground. If a heavy fire condition exists, the IC must anticipate an early collapse and should use an exterior attack. Collapse zones must be established and adhered to. Ventilation will be limited and delayed at best and may not even be attempted safely. Steel-plated buildings also will have higher heat conditions and present a greater overhauling problem due to the limited ventilation.
If conditions are acceptable for interior operations and roof ventilation will be employed, companies on the roof will require metal cutting blades for the saw–and plenty of them. You can expect a ventilation hole of one foot by one foot from a blade before it is worn down. Cutting torches also may be used, but transporting them to and operating them on a roof require time and training.
MASONRY BLOCK-COVERED WINDOWS
Many times basement and rear first-floor windows of commercial buildings are sealed to prevent breaking and entering. Upper-floor windows also may be sealed if the building is being renovated or is vacant. Under fire conditions, attempting to remove these windows for ventilation or stream access becomes a manpower-intensive operation.
At ground level, the old battering ram becomes the tool of choice. It is employed easily, and two firefighters can knock out blocks by swinging the tool. A third member can follow and use a six-foot hook or axe to knock out any debris and clear the window opening. Sledgehammers also can be used, but the ram is more effective. Manpower should be rotated as soon as possible.
Once the covered window is either above or below ground level, the operation becomes more difficult. Below-level tactics will be governed by how much access you have to the opening. A flathead axe or maul might be the only tool you can swing down into the block.
Operations aboveground require a position from which to operate. While working off ground ladders, it is very difficult to take solid swings with hand tools and keep your balance. The preferred method is to work off of an aerial platform, if one is available. This gives you a solid deck from which to work, and the height of the basket can be varied to reach different window levels.
When removing masonry block-covered windows or doorways, always start near the top of the opening. As you knock out blocks, lower the basket and work on the next row–blocks supported on only one side are easier to knock out, and this pattern decreases the possibility of large amounts of block falling at once and injuring firefighters.
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When using a power saw on a roof covered with steel plating, the operator must be aware of several factors: the size of the ventilation hole will be much smaller than normal, the metal cutting blade will be rapidly depleted, a shower of sparks may endanger any exposed personnel, and the potential for collapse due to the added weight is much greater.
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Concrete block windows above ground level are easier to force or operate at using an aerial platform. Because your footing is more stable (working on the platform and with a guardrail to lean against), you can use a more powerful swing than when operating off of a ground ladder. Note the absence of vertical ventilation due to steel plating on the roof and unknown fire conditions underneath.
BOB PRESSLER, a 21-year veteran of the fire service, is a firefighter with Rescue Company No. 3 of the City of New York (NY) Fire Department. He has an associate`s degree in fire protection engineering from Oklahoma State University, is a frequent instructor on a wide range of fire service topics, and is a member of a volunteer department.
