How a Fire Engine Works

I'm Jake O'Neal, creator of Aniamgraffs.  And this is how a fire engine works. 

There are many possible model variations for  different needs, so I've chosen to focus on  

a fairly standard pumper truck designed to  transport crew, tools, water, and pumping  

capabilities to the scene of an incident. First, let's have a look around the exterior.  

Warning lights designed to alert  drivers for safe fire truck passage  

can be changed to steady beams for proper scene  illumination when arriving at a destination. 

The pump on this truck is located mid-ship, though  front or rear mount pumps are also possible. 

Ample rear storage compartments turn this rig  into a mobile toolshed. There are folding steps  

on the back for roof access, where the  hosebed, ladders, and more tools reside. 

Coming around to the front, there's an electronic  speaker for various warning sounds, a preconnected  

hose for quick access when responding to  smaller incidents like trash or car fires,  

there are loud air horns that can sound as  needed by the driver, and a "Federal Q" siren,  

which is a mechanical device that produces  the classic, familiar "wailing" sound. 

Now let's go into more detail,  starting with the pump. 

Some pumps have manual controls for  every task, especially older pump models.  

The intake pressure gauge is a compound  gauge, meaning it can show values below  

atmospheric pressure (or vacuum conditions) when  sucking water up from a pool or mobile tank,  

or positive pressure when connected to a  pressurized source like a fire hydrant. 

Since the truck's engine also drives the  pump, engine temperature, RPMs, fuel,  

and oil pressure are monitored. There's a manual  engine throttle knob to control engine speed. 

A master pressure gauge shows how  much pressure the pump is producing  

combined with existing pressure  from any incoming water supply. 

Various smaller pressure gauges keep track  of the many outlets located around the truck,  

with their corresponding pull handles and  levers to open or close specific outlets. 

There are knobs to divert some water for engine  and pump cooling, as well as pump primer controls. 

The tank filler knob allows incoming water  to enter the built-in tank. There's an air  

chuck connected to an onboard air compressor. A  nearby radio and speaker provides communication  

to the pump operator since they may not be able  to see the fire scene from this side of the truck. 

Supplying sufficient water  pressure to any number of outlets  

from varying supply sources is a difficult  job that requires constant monitoring. So,  

pumper trucks may have different levels  of automation to aid the pump process. 

A digital panel can automatically monitor engine  vitals while also altering engine speed to keep  

pump pressure constant. Electrically controlled  valves can automatically adjust to keep pressure  

at desired levels for specific outputs. And some of the newest systems are highly  

automated, allowing a crew member to divert  attention to other firefighting tasks. 

This particular pump is a  centrally located, midship design.  

It's powered by the diesel  engine through the drive shaft. 

A metal rotating disc with internal fins  called the impeller performs the pumping work.  

The pump is rated up to 3,000  gallons (11,356 liters) per minute,  

which is about 71 average sized  bathtubs full of water every minute. 

2 1/2 to 3 in. diameter hoses  in a crosslay compartment  

allow for quick access from either side,  and may be preconnected for fast deployment.  

A smaller 1 1/2" booster hose on a reel can  be deployed for small fires or used to wash  

hazardous substances from a fire scene  or firefighting gear after an incident. 

The master stream is used when water needs exceed  350 gallons (1591 Liters) per minute, which would  

make a handline too difficult to control. A  smooth bore nozzle can be attached for range,  

or a fog nozzle to create a heat barrier, for  example. The master stream is so powerful that  

it's generally not safe for use while  fire crews are inside a structure. 

There are additional inlets and  outlets on the other side of the pump,  

as well as the front and rear of the apparatus. 

An onboard water tank is situated at  the back of the truck. It can hold  

1,000 gallons (3,785 liters) of water.  However, even a smaller handline hose  

might deplete the supply in 8-10 minutes. The  master stream would empty the tank in 1-3 minutes.  

The tank delivers an instant water supply,  but crews will be hooking up to a fire hydrant  

for anything more than small trash or car fires. The interior of the tank is divided into sections  

with baffle walls to tame the sloshing water  as the truck travels to and from an incident. 

Moving away from the pump and tank,  let's examine the rear storage area.  

Emergency response vehicles carry tools for  the many different incidents they respond to.  

This truck has a basic tool selection  to give you the general idea. 

Starting on the driver's side, there  are assorted hose couplings and nozzles.  

A concrete saw with gear and tool bags. 

The middle compartment has respirator  masks, a so-called fireman's axe with the  

standard chopping blade on one side and a pointed  instrument on the other for digging or prodding,  

a fireman's maul which combines a hammer surface  with a bladed side and a hook in the handle. A  

standard sledgehammer, and a pair of bolt cutters. The last compartment has SCBA (meaning  

"self-contained breathing apparatus")  oxygen tanks and harnesses. 

There are ABC extinguishers. The letters signify  what class of fires the extinguisher can be used  

on. Class A is for items like trash, wood, or  paper. Class B is flammable liquids such as oil,  

gas, paint, and so on. Class C is electrical  equipment. The powder in these extinguishers  

doesn't conduct electricity, making them  effective to fight electrical fires. 

In the passenger side compartments we  have more hose couplings and hoses.  

There's lockout and tagout gear for locking  and labeling circuit breaker terminals or  

main water valves in a building to prevent  tampering during or after an incident.  

Power tools, extension cords,  air hose and pneumatic tools,  

various hydraulic spreading and cutting tools  sometimes referred to as the "jaws of life".  

A purple K extinguisher, which is a dry  chemical extinguisher especially suited  

for class B or flammable liquid fires. There are various tool cases and familiar  

hand tools. A hydrant bag with implements to  operate fire hydrants. A high-rise kit for  

standpipe valves. Standpipes are pipes linked to  the water main inside buildings that function as  

a sort of indoor fire hydrant, giving fire crews  access to water in large or multi-floor buildings.  

The CO2 extinguisher uses carbon dioxide to  effectively push available oxygen out of the way,  

drowning the fire. These extinguishers are used  for electrical fires and sometimes liquid fires.  

A high powered gas fan sits nearby,  which firefighters place at doors or  

openings to remove smoke, heat, or other  combustible elements from a building. 

On top there's hose beds for storing  various hose diameters and lengths.  

An average length of hose is 50 ft (15.2 m). A  pumper might carry something like 800 feet of 2 ½  

inch or larger hose, and 400 feet of 1 ½ to 2  inch hose. For comparison, the standard city  

block in the U.S. is 660 ft. on one side. Also on top, there's ladder storage. On the  

driver's side there are hard  suction hoses for drafting. 

Drafting means pulling water from a standing  water source like a pool, pond, or portable tank.  

When multiple emergency vehicles  respond to one incident,  

tanker trucks may deliver water to a portable  reservoir that other pumper trucks can draft from. 

Now let's head to the front of  the apparatus, inside the cab. 

The driver is tasked with safe driving to and  from an incident. The large nearby switchbank  

governs many standard items you might find on  large trucks of a similar size. There's also a  

push button gear shifter. A central panel with  a screen monitors truck specific functions but  

can also control many additional presets, for  example, for different external lighting schemes.  

A pull cord sounds the loud horns,  

and a foot pedal controls the previously  shown Federal Q mechanical siren. The  

driver uses the road-to-pump switch to safely  engage the pump when the truck is stopped.

The officer rides on the passenger side  and handles things like siren control,  

external radio communications,  the public address speaker,  

and command laptop. There's also  an officer's side speedometer. 

Crew members sit in special fire seats with a  bracket and support padding that allows oxygen  

canisters to be safely worn while riding to an  incident. Brackets overhead stow firefighting  

hardhats. There are headsets for communication,  handheld radios, and flashlights for crew members.