Why does the fire truck driver's seat not have an air tank?

Question of the Month: (June/July 2010)

"My daughter, who is in kindergarten, recently visited the fire station with her class and was trying to explain why the driver's seat didn't have an air tank for fighting fires like all the other seats had. Will you please help explain that to me as I'm not quite sure why this would be?"

We often get asked this question from both kids and adults alike as they climb aboard one of our fire engines or ladder truck and notice that indeed, the driver's seat is missing an air pack (self-contained breathing apparatus or SCBA). The driver, who is a firefighter and also an engineer-driver, or engineer for short, is responsible for the operation and all functions of the truck. It is often referred to as "his/her truck" for that incident or shift. Therefore, s/he will typically not be tasked with working the hose and actual suppression of the fire so no air pack is stored behind their seat.

The engineer is responsible for setting up the truck for operations and ensuring that a water supply is established and maintained throughout the incident. The water source may come from several locations. From water carried on the truck (anywhere from 300 to 1,800 gallons depending on the type of truck), water pumped from another truck, hooking directly to a fire hydrant, or using a water containment device such as a "dump tank" supplied from water tenders, or even drafting water from a swimming pool, stream or pond. The engineer then remains with the truck throughout the fire if it has been assigned to supplying water. Although some trucks have an engineer's platform directly behind the passenger cab, most trucks have the controls and pressure gauges just behind the cab, on the driver's side, for easy access.

An integral and extremely important responsibility of the engineer is to monitor and adjust water levels and pressure of each hose line. Hose length, diameter, type and level of grade the hose rests on, all play major factors in providing an effective water flow to the nozzle and suppression of the fire. Too little pressure can make the force of water exiting the nozzle ineffective for use in containing or suppressing a fire and in some rare cases, from even reaching the fire at all.

Too much pressure may cause so much force at the nozzle end that when it is opened to spray, it can actually lift the firefighter off the ground and possibly lose control. This is extremely dangerous and is why the pressure must be monitored at all times. Frequent communication between those on the nozzle and the engineer must be possible as fluctuations in pressure can occur at any time. Several years ago, while working on a large house fire in the Hayden Lake area, one firefighter was actually lifted off the ground and was forced backward and through a neighboring house's picture window when an unexpected pressure change in his hose occurred. Though not hurt and able to continue fighting the fire, flying through the air through windows, unannounced and unaware, is not the safest or suggested method for putting out a fire.

There are times when a truck may arrive and it is not needed to pump or supply water. The incident commander may assign its crew to myriad other tasks, many requiring the use of an air pack. Almost all fire trucks carry spare air packs and bottles so the engineer (who is also a firefighter) has access to one if necessary.

I hope this helps clear up the reason driver's seats in fire engines typically do not have an air pack.

Stay safe out there!

Jim Lyon is the public education specialist/information officer with Kootenai County Fire and Rescue (KCFR). If you have a question about emergency services in your area, please submit your question to "Ask Firefighter Jim" at [email protected]. Visit our Web page at www.kootenaifire.com for additional information and to read archives of previously answered questions under the link, "Prevention."

Elevation decreases water pressure, so if fighting a fire up a hill or in a high rise, a tremendous amount of force is necessary at the ground level (at the truck) to allow for an effective water flow at the nozzle.

Water pressure in a fire hose is calculated in pounds per square inch (psi). In using a 1 3/4 inch diameter hose line, the pressure at the pump necessary to have 100 psi at the nozzle is between 140 psi and 150 psi.

For determining how much pressure is necessary to supply water at 100 psi at the nozzle when used in elevated situations, such as a high rise, a general rule of thumb is an additional 5 psi per floor. Therefore, to push water up 30 flights of stairs would require pressure at the pump of approximately 300 psi.