Determining whether a fire will start and, if it does, how far it will spread

The manner in which a facility is constructed will play a large role in determining whether a fire will start and, if it does, how far it will spread.

(i) Fire-receptiveness of the material. Although no material can be considered “fireproof” in an absolute sense, given materials vary considerably in the ease with which they ignite or their ability to withstand heat from a fire.

These varying degrees of fire receptiveness may not be intuitively obvious: unprotected steel, for example, may bend and eventually give way when exposed to fire, whereas heavy wood beams may char on the outside but they burn no further (the char serves as insulation).

Engineers and architects should take these receptiveness variations into account when designing and remodeling buildings.

(ii) Materials also vary a great deal in the amount of smoke they give off when they do burn. This can be very important because smoke and toxic gases kill more fire victims than flames do. Many people view plastics and other synthetic materials as particularly risky.

There can be no doubt that some of these materials do present substantial hazards, spreading heavy, acrid, deadly fumes so fast that victims are overcome before they can react. It is also true; however, that research has provided plastic and synthetic materials that are much less dangerous.

It is quite important, therefore, that the persons in charge of selecting construction materials and furnishing be aware of both how easily a given material will burn and how much smoke it will give off.

(iii) Fire-containment qualities of a structure are important. When buildings can be compartmentalized, a fire may be contained within a given area. Rooms may be separated from one another by doors, and when these are fire resistant and fairly airtight, both the fire is the smoke and toxic gases may be contained for some time (ideally until the fire department comes).

But doors are not the only openings between rooms. Since the ventilation system is set up for the very purpose of moving air between rooms, special controls are needed to see that fumes are not quickly spread throughout the building. Fire doors are also used for this purpose.

Walls penetrated by openings for electrical cables, plumbing, and ventilation ducts, and security and alarm wiring could pose containment problems. If these opening can be sealed with so-called fire stop material (a heat-resistant, putty-like substance), fire copayment will be enhanced.

Of course, this precaution should not be forgotten when remodeling or retrofitting (e. g., running new wires for a computer system).

(iv) Layout-should also be considered part of construction. The location, number and accessibility of stairwells and outside exit doors will affect the ease of evacuating building occupants as well as the ability of fire fighters to get to the seat of the fire, proper design in these areas requires that studies be made of population densities and flow rates: a common rule of thumb is that every building section should have two exit paths, excluding elevators.

Naturally, the stairwells should be self contained and fire resistant and, if possible, pressurized to keep out the smoke.