THE ROLE OF THE BOOSTER TANK IN STRUCTURAL FIRE ATTACK
THE ENGINE COMPANY
You are a newly promoted lieutenant of an engine company that has just been dispatched to a reported house fire. The unfamiliar name of the street on which the fire is reported leads you to suspect that it must be in one of those new housing developments on the outskirts of town. Your crew, consisting of a driver/engineer and one firefighter. quickly makes its way to the pumper while you check the map and acknowledge the alarm over the radio. The map confirms your suspicion: The fire is in a new subdivision, and your company will Ire first to arrive if you can figure out how to get there. That won’t be easy: this development is typical of new suburban areas: It consists of a confusing maze of cul-de-sacs and winding streets. As the apparatus nears the entrance to the subdivision, your fears of not finding the unfamiliar address ease slightly when you see that it can be found by heading toward the rising column of smoke.
With the second engine and battalion chief a good six or seven minutes behind, you know that you will have to assume command of this fire before the chief arrives and begin operations with your three-member company. As the first officer at the fire scene, you realize the decisions you make in the first few critical minutes of this incident will profoundly influence the outcome of the overall operation.
SUPPLYING WATER
You, however, will have to make your first big decision before you’re actually at the fire scene. You must decide if your company will stop at the closest hydrant, which is at least 500 feet away, and forward lay a supply line to the fire. The pressure is on: the decision you must make here can have disastrous consequences if you are wrong. Do you stop at this hydrant and lay in your own supply line or do you go directly to the fire and initiate a quick attack with water from the booster tank? You quickly weigh the pros and cons of each option. Laying in your own supply line will provide a continuous supply of water but at the expense of your only firefighter, who will have to stay at the hydrant until you are ready for him to charge the supply line. This will delay your attack on the fire. If you go for a quick attack, there’s a good chance you’ll knock down the fire w ith the booster tank. But. what if the water runs out before the second engine can lay a supply line?
Every day. fire companies achieve rapid knockdown, if not complete extinguishment, of structure fires with the water carried on their apparatus. Departments in rural areas usually have no choice: hydrants and static water sources are seldom available. Engines equipped with booster tanks allow big city and suburban fire departments to quickly control a significant number of fires before hoselines are laid to or from hydrants, because most fires are relatively small and do not require a large amount of water to bring them under control.
Rapid control of fires has been made possible by three developments, which changed the modern fire service: large (500to 1,000-gallon) water tanks on pumping apparatus, preconnected attack hoselines, and self-contained breathing apparatus. These innovations allow an engine company to spot its apparatus at the fire building, rapidly deploy a hoseline, and direct hundreds of gallons of water to the seat of the fire.
When a quick attack with tank water is appropriate and successful, the results are impressive: The fire is knocked down in the time it normally would take a company to lay a hoseline to or from a hydrant. When a quick attack is unsuccessful, the results can be disastrous: The fire burns out of control, endangering personnel who have exhausted their limited water supply.
The keys to safely and successfully using a booster tank are the following:
- Know when—and when not—to use it.
- Know how to use its limited water supply most effectively.
- Ensure that a backup supply is available.
A TOUGH CALL
Every decision a fire officer makes is only as good as the information on which it is based. Unfortunately, many critical decisions in our business have to be made with insufficient information. The decision to connect to a hydrant or initiate a quick attack w ith tank water is one of the most difficult for the officer of the engine company first to arrive at a working structure fire. The chances of making the right call depend on the officer’s experience and the information, or factors, taken into consideration.
(Photos by Doug Wolf.)
The following factors will influence this critical decision.
Safely. A quick attack, using tank water and preconnected lines, may be easier for firefighters who otherwise would perform a hoselay to or from a hydrant. It is, however, harder on their officer, who must shoulder the added responsibility for the safety of the crew operating with a finite supply of water. The officer must be constantly and intently ‘aware of the crew’s position, escape routes, the volume of water being flowed, and the quantity of water remaining in the tank. It is irresponsible for an officer to commit personnel to a position where safe withdrawal could possibly depend on a continuous supply of water that is not available. In practical temis, don’t send a crew into a smoky furniture store and hope it has enough water to get back out.
Experience. If you reflect on your personal experience and the experience of your department, you probably will recall two important lessons that will influence your decisions concerning fire attack and water supply:
Lesson A: Fires in structures of similar size, construction, and occupancy generally require the same amount of water to control.
Lesson B: Things occasionally go wrong. Every department has its own horror stories about the “routine” fire that got out of hand because it was underestimated or the second engine did not arrive when expected because it had gotten into an accident.
Occupancy and life hazard. Although a quick attack with tank water can be appropriate for other occupancies, it is particularly effective for fires in oneand two-family dwellings. Early detection, fire load, and compartmentation common to these residences tend to limit the fire to a size that often is possible to bring under control with a few hundred gallons of water. The life hazard of such occupancies requires a rapid and aggressive attack on the fire, whieh is the most effective means for an engine company to save lives. The size and fire load of multifamily, commercial, and industrial occupancies make them less likely candidates for a quick attack with a booster tank.
Size of fire. The size of a fire will determine the flow of water (gpm) necessary for control and the period of time the supply in the booster tank will last. As a practical matter, a fire involving one or two rooms in a house usually can be controlled by one 1¾inch attack line flowing 150 gpm for three minutes. This flow rate (150 gpm x 3 minutes = 450 gallons) is within the capacity of most booster tanks. Calculating flow rates is, at best, an inexact science that depends on too many variables and unknowns. When it comes to determining if a fire can be controlled with tank water, theoretical calculations are no substitute for practical experience.
Construction. How much a structure itself contributes to the fire load of a building directly determines the amount of water necessary to control a fire. For example, it is entirely possible to control an advanced fire in a one-story, 1,600-square-foot house con slructed with masonry bearing walls with 750 gallons of water. This is basically a con tents fire; structural components contribute little fuel to the fire until it extends to the attic. In contrast, an advanced fire in a wood-frame structure of similar size typically requires a rate of flow that exceeds the capacity of most booster tanks.
Is fire showing through the roof ? As mentioned earlier, the eompartmentation and fireloading of oneand two-family residences tend to limit a fire to a size that often can be controlled by a booster tank. These favorable characteristics are nullified once fire has burned a hole in the roof. A manage able fire involving one or two rooms suddenly becomes a different animal once it spreads to the attic and vents itself. A fire showing through the roof will defy a quick attack and rapidly exhaust the water in a booster tank. When a fire has progressed to this point, its water-flow requirements far exceed the capacity of a booster tank. There are three reasons for this dramatic increase in demand for water:
- Once a fire reaches the attic, it is no longer confined by any walls. The fire is free to spread, unimpeded, over every rtxmi in the house.
- When a fire in a room spreads to the attic, it quickly changes from a contents fire to a structure fire, feeding on a generous supply of wood trusses or rafters.
- The hole in the roof may be beneficial in terms of ventilation, but it increases the amount of water needed to control the fire because it allows expanding steam to escape. Steam converted from hose streams enhances the extinguishing properties of water by suppressing fire that is remote from the point of water application.
Exposures. The extent to which exposures are threatened can prompt an engine company officer to establish a continuous supply of water by connecting to a hydrant. The potential for a fire to spread must be considered in decisions concerning fire attack and water supply.
Personnel. The number of personnel riding an engine can determine the options available to its officer. For example, a four-member engine company (officer, engineer, two firefighters) can commit a firefighter to “hydrantman,” lay a large-diameter supply hose to the fire, and still have an officer and firefighter ready to advance a handline operating initially on lank water. This is not possible with a three-member company; the officer can be forced to choose between quickly attacking a fire or establishing a continuous supply of water.
Capacity of booster tank. Tank capacity directly determines the duration of water supply at a given rate of flow. The advantage of a large tank is obvious. For example, a company flowing 150 gpm can be sustained for three minutes with a 500-gallon tank. At the same rate of llow, a 750-gallon tank will sustain the company for five minutes; a 1,000-gallon tank will last almost seven minutes.
Availability and spat ini; of hydrants. An officer does not have to choose between a quick attack and a continuous supply of water when hydrants are spaced a few hundred feet apart. The engine company can spot its apparatus at the fire building and begin firefighting with the booster tank. After charging the handlines, the engineer can hand-lay a supply line to a nearby hydrant.
Estimated time of arrival of second-due engine. Although a significant number of structure fires are extinguished with booster tanks, the tanks should seldom be relied on as a stand-alone water source. An officer operating with a booster tank must be constantly aware of how long it will take for the water supply to be augmented by another engine.
The decision to initiate a fast attack with the booster tank should be strongly influenced by how long it will take the seconddue engine to provide a secondary source of water. An engine officer should answer the following questions before choosing to attack a structure fire with a booster tank:
- Do I have enough water to put out this fire?
- If not, how long will it take another company to augment my supply?
- What is my contingency plan if that company is delayed (due to traffic, trains, accident, or breakdown)?
A common mistake when using a booster tank is to forsake fire control to conserve water. Every fire requires a certain rate o>f water application for control (sometimes called “critical flow rate”). Water applied at less than the minimum rate is wasted. Remember, the primary objective is to put out the fire, not save water (obviously, the water still must be used judiciously).
A limited supply of water is most effective when applied from a hoseline taken inside the unburned portion of a structure. This position gives the engine company its best shot at saving a life. Any occupants still alive most likely will be found where the fire is not burning. Operating a hoseline at this point can protect occupants and stop the spread of fire. An exterior attack on the burning portion of a structure actually can spread a fire by pushing it into unburned areas. Water applied from the burning side can be wasted on property already destroyed.
The booster tank is an excellent source of water that can be used in structural fire attack, particularly for smaller single-family dwellings. Its effective and safe use depends on having in command an officer who fully understands its limitations as well as its capabilities.
