ROOF OPERATIONS, PART 1
BY TOM BRENNAN
During the next few months, we are going to talk about things we all should nod in agreement on and should be familiar with. However, the important point is that most of them when ignored or improperly accomplished can still cause unplanned for fire loss and injuries to firefighters that are sometimes fatal.
When and why do you cut a roof?
The first part is simple: You cut a roof when the fire is under the roof–when the fire is on the top floor (remember: one-story buildings always have top-floor fires!). In short, if the fire is not “read” by the firefighter assigned to vertical ventilation as being on the top floor, don`t take the saw!
So with all the time we can spend (and we will soon) on roof operations, let`s stick with the second basic question: Why do you cut the roof? The first two remarks should be routine answers: (1) to quickly retard the horizontal spread of fire by rechanneling it to where it wants to go–straight up over itself and (2) to reduce the atmosphere below from intolerable to operational so aggressive firefighters can continue their interior attack and have more time to find trapped victims.
Today, we seem to have a “new” problem that is surprising and injuring and killing firefighters: smoke explosion in the cockloft space. It is NOT new, and prompt and proper cutting of the roof membrane almost always before the ceiling is pulled on the fire floor below is the only way to cause this possible fireball explosion to be a non-event. Combustible, flammable, and explosive by-products of combustion are forced into and are trapped within spaces in the fire compartment and surrounding areas.
Of particular importance is the large, open space–the cockloft. Here, if the ceiling membrane fails–either from the fire or from being removed by firefighters from below before the heated and pressurized gases are allowed to escape to the outer air from an opening cut by the roof team–the pressure force will push down the remaining ceiling membrane. Sometimes the falling membrane will be accompanied by a large fireball that will cause a flashover of the area on which it lands. Now fire has extended to exposures and, in many cases, traps examining firefighters between their work area and the exit they knew was there a moment ago.
With today`s concern for energy conservation in the areas that need heat as well as the southern air-conditioned structures, buildings are built tighter and tighter with flimsier materials. Explosive by-products of fires are more easily forced into these spaces and are “pushed” for great distances–so great that the gases remain explosive but have greatly cooled. They are above the areas that a few years ago would have been considered safe from extension. Now additional phenomena labeled “cold smoke explosions” occur with the same results. The energy is slightly delayed, however, as the vapor needs the traveling heat from the fire area as well as the air to cause it to “blow.”
With all that said, roof cutting is more important now than ever before–and at a time when we have fewer and fewer performers to accomplish that task in time to be effective.
Enclosures found on the roof are known
as bulkheads.
These enclosures are large constructs with doors in them for the maintenance crews` or owner`s entry and exit. When they are over the stair enclosure to a dwelling, they become a primary target for the roof team. They are secondary targets when they appear on the roof as the top of the elevator shaft, incinerator, or compactor shaft. The doors to elevator and garbage chutes are fastened closed by locks; the stair shaft enclosures are fastened closed by simple latches without a key (the law). However, all the doors have self-closing springs that keep them from staying open once they are opened.
What do you do to keep the door open and be able to go about your tasks? Leave a tool? Nah! You need it elsewhere. Find something on the roof, such as a cement block, coping tile, or tar pot–anything to keep it open. If debris is not available, break the top hinge of the door. Put a tool in the top of the door and slam it shut. The door will lose its integrity (for the same reason you start with the bottom hinge on the doors to the fire apartment) and “hang” open for you.
A small skylight is usually above the bulkheads over stairs. If the smoke is just easing out, leave it. But if the smoke is coming out of the door opening with edges on it, you have to do something else. How do you get to the skylight that is seven to eight feet over your head? Simple. Break the other hinge on the door, slam the halligan point into the roof as a stop for the door, and lean the door against the bulkhead. With a short run, you hit the door with one foot at the latch and bingo! you are on the bulkhead.
More roof operations next month. n
n TOM BRENNAN has more than 35 years of fire service experience. His career spans more than 20 years with the City of New York (NY) Fire Department as well as four years as chief of the Waterbury (CT) Fire Department. He was the editor of Fire Engineering for eight years and currently is a technical editor. He is co-editor of The Fire Chief`s Handbook, Fifth Edition (Fire Engineering Books, 1995). He is the recipient of the 1998 Fire Engineering Lifetime Achievement Award.
