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Fire Fighting

 

Before a fire is to be extinguished, it must be classed so that the correct extinguishing agent and method is used. Use of an incorrect agent or method may be ineffective or dangerous.

Other factors to be considered before fighting a fire are:

  1. The size of the fire;
  2. Accessibility;
  3. The risk of escape being blocked;
  4. Hazards in or produced by the fire;
  5. Material around the fire that could be at risk from the fire (exposures);
  6. Possible changes to the ventilation system caused by the fire;
  7. Possible side effects of fighting the fire;
  8. The equipment available.

When a fire is burning in a confined area, care must be taken to prevent extra oxygen from reaching the fire. As well as smoke being potentially explosive, a fire that starves of oxygen will produce carbon monoxide, instead of carbon dioxide, which is explosive when mixed in the right proportions with oxygen. If possible, the smoke from the fire should be exhausted from a high part of the area before entry is made in a low part of the area, this is known as ventilating high and entering low.

Electrical transformers on fire present a great hazard other than the risk of electrocution because they contain oil that is potentially explosive as well as highly poisonous and corrosive.

Pressure storage vessels containing flammable liquids or gases present a particular danger in a fire. Flames touching the vessel will cause the temperature of the liquid part of the contents to rise and produce more of the vapour or gas part, increasing the pressure inside the vessel. When the pressure reaches a certain point, a relief valve will open to allow the vapour or gas to escape. As the vapour or gas escapes, more of the liquid changes to vapour or gas with the result that the level of the liquid in the vessel drops. Once the level of the liquid has dropped to below the point where the flames are touching, the vapour or gas itself will be heated. If heated sufficiently, the vapour or gas will expand faster than the pressure relief can allow it to escape, until a point is reached where the vessel is unable to contain the pressure and ruptures.

This is known as a Boiling Liquid Expanding Vapour Explosion (BLEVE), and its results are quite catastrophic.

Any pressure storage vessel that has been involved in a fire must be treated with extreme caution and thoroughly cooled. Cylinders should be immersed in water for 24 hours and then tested.

Vehicle tyres are in effect pressure storage vessels and can explode in a similar manner to a BLEVE with potentially devastating results.

 

Product

Flash

Point

Auto -

Ignition

Temp.

Density

at 15oC

Propane

N.A.

(Gas)

500oC

0.510

Petrol

(unleaded)

-43oC

390oC

0.725

Crude Oil

(Bass Strait)

-15oC

350oC

0.796

Lighting

Kerosene

48oC

380oC

0.790

Mineral

Turpentine

32oC

250oC

0.820

Industrial

Diesel

80oC

360oC

0.855

Bitumen

210oC

480oC

1.020

Lubricating

Oil (SAE 20)

210oC

410oC

0.890

Water

   

1.000

 

 

Extinguishing Agents

Water

Water has the effect of removing heat from a fire, plus the steam produced helps exclude oxygen. It is very effective in fighting A class fires and quite effective on B class fires, but should never be used on D and [E] class fires. Water can be projected a great distance, or used as a curtain to protect fire-fighters or exposures. The cooling property of water is very effective in preventing an extinguished fire from re-igniting.

Water is best applied as a spray to increase the surface area of the water acting on the fire which improves the cooling effect and leads to the production of more steam. This also minimises the risk of scattering the contents of the fire.

The risks involved in fighting fire with water are:

  1. Electrocution;
  2. Scalding from steam;
  3. Heat exhaustion from raised humidity;
  4. Damage caused by the use of high pressure jets;
  5. Flooding.

Dry Chemical

Dry chemicals are probably the most useful extinguishing agents. They are effective and can safely be used on any class of fire, the chemical can be projected a fair distance (being moderately affected by wind) allowing a fire to be fought with minimal risk, and there are no toxic by-products from its use.

The most common chemical used is monammonium phosphate powder, also known as AB(E) powder, and is very effective on A & B class fires and moderately effective on C class fires. Sodium Bicarbonate, also known as B(E) powder, is only moderately effective on A class fires but is extremely effective on B class fires and very effective on C class fires.

Dry chemicals work by combining with flammable gases to form non-flammable gases, thus quickly interrupting the chemical reaction of the fire. They also have some blanketing effect for preventing a fire from re-igniting.

The only drawbacks from using dry chemical are that they are quite messy, which can be a problem when used on electrical equipment and for visibility, and they have no cooling effect for preventing hot material from re-igniting.

Vaporising Liquids (halon type)

As halons are an ozone depleting substance, the use of this extinguishing agent after 31st December 1995 has been banned.

Halons, the most common used being Bromochlorodifluoromethane (BCF), are an extremely effective extinguishing agent. The air being drawn by a fire only needs to be 5% BCF for the fire to be extinguished. Halons can be used on any class of fire, but are most effective on B and C class fires. They work by combining with flammable gases to form non-flammable gases, plus they have some cooling effect. The most useful aspect of vaporising liquids is that they leave no residue.

The main problem associated with the use of halons is that the non-flammable gases that are created are highly toxic. Also, vaporising liquids will not keep the remains of a fire cool and they are affected by wind.

Vaporising Liquids (non-halon type)

There are a number of environmentally friendly vaporising liquids available. Generally, they are much more effective than carbon dioxide but not as effective as dry chemical or halon and do not produce dangerous levels of toxic gases.

Carbon Dioxide

Carbon dioxide is safe to use on any class of fire, but is only effective on small fires due to its short range and the fact that it disperses quickly. Its main advantage is that it leaves no residue.

Carbon dioxide works by excluding oxygen from a fire and by cooling. It is substantially affected by wind and can cause injury and damage to equipment from the extreme coldness produced.

Carbon dioxide is fairly effective in fixed systems for enclosed spaces but creates a toxic atmosphere to dilute air sufficiently for extinguishment. An alternative, known as Inergen, very effectively extinguishes fires when used to dilute air to a survivable level and doesn’t create a toxic atmosphere.

Low Expansion Foam

Low expansion foam is very effective on A and B class fires, but has no use on any other class. It works by smothering a fire to exclude oxygen, and forms a blanket (or film) to contain flammable vapours (which are heavier than air) and cool the remains of the fire. It is particularly useful in preventing re-ignition and is often applied after a fire has been extinguished with dry chemical.

Low expansion foam is basically a detergent that is mixed with water. Special detergents have been developed for fire fighting, and the many types (some organic, some synthetic) all have different properties which have benefits in different situations. The most commonly used low expansion foam is the synthetic Aqueous Film Forming Foam (AFFF) because it has the widest range of the desired properties of foam.

AFFF should not be used on alcohol fires as the alcohol breaks down the film. Alcohol resistant foams are available.

Low expansion foam is normally aerated as it is produced and typically has an expansion ratio of about 10:1 (ie ten cubic metres of foam will be produced from one cubic metre of mixture), however unaerated foam is still useful for its film forming properties.

When fighting a fire with low expansion foam, the appliance should first be aimed to the side of the fire until correctly made foam is produced, then slowly worked across the fire to form a blanket. The film that is produced by the decomposition of the foam must not be broken if re-ignition is to be prevented.

As low expansion foam is applied at a lower pressure than water, and a lower volume of water is required to extinguish a fire, there are fewer risks of damage and flooding than in the use of water. Also, less steam is produced when fighting fire with low expansion foam than water, but the risk of electrocution is the same as for water.

High Expansion Foam

High expansion foam is produced by a machine called a high expansion foam generator, and typically has an expansion ratio of about 1200:1. Its main use is for fighting fires in confined inaccessible places, but is only moderately effective. It is applied by allowing the foam generated to unroll a length a plastic ducting which is burnt off by the fire to allow the area to be filled with foam to suffocate and cool the fire.

Wet Chemical

This extinguishing agent is designed exclusively for use in kitchens on fires involving animal fats and vegetable oils (F class fires). It works by converting the oils or fats into soap and can be used in either a fixed or hand-held system.

 

Fire Extinguishers

Hand held fire extinguishers are designed to be a first response to a fire before it becomes any larger, but are useful in certain other situations. Larger trolley mounted and vehicle mounted extinguishers are very useful in many situations. The important factors in determining whether or not an extinguisher will be effective on a particular type and size of fire are the type of extinguishing agent and how much of and how quickly the agent can be applied to the fire.

All sizes of all types of hand held fire extinguishers are tested on standard A and B class fires and given a rating for each (if successful). An example of an extinguisher's rating would be 5A:40B:(E). This extinguisher would be in the middle of the range for both classes of fire in terms of which standard fires it extinguished, the (E) rating means that it is safe to use on electrical fires. A rating of 1 would indicate that the extinguisher only extinguished the smallest of the standard A class fires. Having no rating for either A or B class fire doesn't mean that that extinguisher can't be used on that class, only that it wasn't able to extinguish any of the standard fires for that class.

In addition to the ratings, fire extinguishers are colour coded to show what type of extinguishing agent they contain:

	Agent			Colour

Water				Red
Dry Chemical			Red with white band
Carbon Dioxide			Red with black band
Non-halon Vaporising Liquid	Red with yellow band
Halon type Vaporising Liquid	Yellow
Foam				Blue
Wet Chemical			Brown

Before attempting to use a fire extinguisher, it is important to check that it is full and that it works. Water, foam and dry chemical extinguishers have a small pressure gauge to indicate their level of charge, and these and the other types can be checked by their weight. Also, the presence of the safety clip in the trigger can be checked.

Extinguishers should be tested before a fire is approached, this also gives the user a feel for the extinguisher's range.

Different extinguishers have different types of nozzles and it is important to be aware of the usage of the nozzle, especially with foam and carbon dioxide extinguishers.

The nozzle on a foam extinguisher is designed to aerate the foam and care must be taken to avoid covering the back of the nozzle with the hand.

Carbon dioxide extinguishers have a very large nozzle designed to protect the user from injury from the coldness of the carbon dioxide as it is released, the hand should be kept back from the guard when the extinguisher is used.

When attacking a fire with a fire extinguisher, the fire fighter should if possible work from upwind, keeping low and start applying the extinguishing agent at the point of the extinguishers maximum range.

Used fire extinguishers are always laid on their sides to avoid confusing them with full ones.

The following table lists the classes of fires with the extinguishing agents that can be used on them in order of preference (assuming that an extinguisher is available for the particular size of fire). Only non-halon vaporising liquids are referred to and dry chemical is listed last for electrical due to the mess.

 

Class

Agent

A

Water

AB(E) powder

Foam

Wet chemical

Vaporising liquid

B(E) powder

Carbon dioxide

B

Dry chemical

Foam

Vaporising liquid

Water

Carbon Dioxide

C

Dry chemical

Vaporising liquid

D

Sand

Dry chemical

(E)

Vaporising liquid

Carbon dioxide

Dry chemical

F

Wet chemical

B(E) powder

Carbon dioxide

 

The following table shows the characteristics of different sizes of the different types of fire extinguishers (trolley mounted extinguishers are not rated):

 

Type

Capacity

Range

(m)

Discharge

time

(seconds)

Rating

Water

9l

6

60

3A

Foam

9l

50l

4.5

15

30

50

3A:20B

Dry

Chemical

2.5kg

9kg

50kg

3

6

6

11

20

30

2A:30B:(E)

6A:80B:(E)

Halon

3kg

11kg

45kg

6

6

6

8

20

24

1A:20B:(E)

2A:80B:(E)

Carbon

Dioxide

3.5kg

5kg

1.5

2

14

22

5B:(E)

5B:(E)

 

Fire Hoses

Fire hoses are used to deliver large volumes of water when fire extinguishers are ineffective or when exposures need to be protected. There are two sizes of fire hose used, 64mm and 38mm diameter, in a standard length of 30m. A line of hose is more than one length joined together.

64mm hose will deliver a larger volume of water at a higher pressure than 38mm hose, but is much harder to manoeuvre, and for this reason a length of 38mm hose is often used as the last in a line of hose. The rule of thumb for friction loss in 64mm hose is 0.2 bar per length, 38mm hose will have a higher friction loss. The usual couplings used are British Instant Couplings (BIC) and are usually made of brass which is corrosion resistant, heat resistant and will not cause a spark.

A usable fire hose is always rolled up with the female coupling innermost (after the water has been drained out) and a damaged hose is always rolled up opposite to this. Should a hose that is rolled up normally be found to be unserviceable, it can be identified by tying a knot in it just behind the male coupling.

Before picking up a length of fire hose, the binding on the couplings should be checked and the female coupling should be checked for the presence of the rubber seal and the freeness of the lugs. A fire hose should always be carried on the shoulder with the male coupling just in front of the shoulder.

A fire hose is unrolled by having one person secure the male coupling while another holds the female coupling by the lugs and runs with it. A person running a second length of hose should have the male coupling on the ground for the person running the first length to secure with his foot before the first length has been completely run out.

Fire hoses should always be treated with care. They should be dragged as little as possible, and the couplings should not be dropped. Should a fire hose fail under pressure, a replacement should be run out beside it before the water is turned off.

 

Fire Hose Appliances

Hydrants

A fire hydrant is the supply point, whether free standing or on a truck. Before a hose is connected to a hydrant, the hydrant should be turned on to ensure that there is clear water available, and the presence of the rubber seal should be checked. The hydrant man can perform these checks while securing the first length of hose with his foot.

Branches

A branch is the appliance used on the end of a line of hose to add velocity to the water flow and control its direction and spray type. A branch man must hold the branch securely and have a back-up man supporting him and the hose.

There are four types of branch:

Straight through	Jet only.
Diffuser		Water can be varied between a
			jet and a curtain (some
			diffuser branches are designed
			to also aerate foam).
Combination		Water can be varied between a
			jet and a spray, with a
			separate outlet for a curtain.
Foam			Allows for aeration of low
			expansion foam.

Inductors

An inductor is used to introduce low expansion foam concentrate into the water flow. Either an in-line inductor can be used where the last hose joins the second-last, or the foam branch can have a built in inductor. Some inductors allow the mixing rate to be varied whereas others don't, the normal rate is 3%.

Dividing Breech Piece

A dividing breech piece is used to split one line of hose into two. A dividing breech piece can be either controlled or uncontrolled. A controlled unit has a valve on each outlet, so once fitted to a line of hose with the valves off, the hydrant can be turned on.

Collecting Breech

A collecting breech is used to bring two lines of hose together into one for increased water pressure. The easiest way to distinguish a collecting breech from a dividing breech is to remember that the female coupling always points to the fire, ie a collecting breech has two male couplings and one female coupling as opposed to a dividing breech having one male coupling and two female couplings.

Monitor

A monitor is a free standing branch that can handle large volumes of water.

 

Signals

Most signals are given by the back-up man upon instruction from the branch man and returned by the hydrant man before being executed. A man on a controlled dividing breech piece will give the 'water on' signal to the hydrant man who then moves up to the dividing breech piece. In the event of a hose failure, the captain will give the signals, and it is he who will signal 'water off' and 'make-up' when he is satisfied that the fire is completely extinguished (the remains of the fire must be turned over and cool).

In an underground situation, there must be a man at each intersection and signals will be passed down the line.

Surface

Water On		Right arm raised with fist
			clenched.
Water Off		Right arm moved from side to
			side at waist height.
Increase Pressure	Right arm held out straight
			to the side with the palm up
			and moved up and down.
Decrease Pressure	Same as above with palm down
			and arm moved down then up.
Make-Up			Both arms curled up and down in
			front of the body.

Underground

	Water On		3 pause 2
	Water Off		3 pause 3
	Bring Another Hose	5
	Check Your Oxygen	6

 

Procedural Example

Running Fire Hoses

  1. The team captain briefs his team on the procedures that he wants the team to follow, such as the positioning of the dividing breech piece, with emphasis on the safety considerations such as not advancing past the exposure until it is protected. He nominates the individual duties of each team member, and when the team has indicated that they have no questions he gives the command "Go".
  2. The branchman on the hose that will be running straight water to protect the exposure runs the first length of hose from the hydrant, while the hydrant man secures the end with his foot. All of the team other than the hydrant man run beside him. Once the second length of hose has been run, he will secure the end of the hose that his back-up man will run.
  3. The hydrant man checks the hydrant for clean water flow and the presence of the O-ring then connects the hose.
  4. The branchman on the hose that will be fighting the fire, usually using low expansion foam, runs the second length of hose then secures the end of the hose that his back-up man will run.
  5. The back-up man on the protection hose runs his hose, flaking it to ensure that he remains a safe distance from the exposure.
  6. The captain, who has carried the dividing breech piece and the branches, gives the "Water On" signal to the hydrant man just before fitting the dividing breech piece and checking that the valves on it are closed. He then begins supervising.
  7. The branchman on the protection hose connects his hose, collects his branch and joins his back-up man.
  8. After turning the hydrant on, the hydrant man carries the foam inductor and the foam concentrate (if applicable) to the dividing breech piece which he will control.
  9. Once the exposure is being protected (the valve on the dividing breech piece having been opened by the attack branchman or the hydrant man), the attack back-up man can proceed to run his hose, flaking as necessary. Once the inductor (if applicable) and his hose are connected, the attack branchman can join his back-up man.
  10. As the fire begins to be brought under control, it may be desirable to bring the protection hose to bear on the fire (not if foam has been used), or to shut it off if there is a casualty to be attended to.
  11. Once an A class fire has been extinguished, the captain will ask for one hose to be shut off (if not already done) and the pressure reduced on the remaining hose. He will then instruct a team member to use a bar to turn over the contents of the fire while water or foam is gently run over them.
  12. Once the captain is satisfied that the fire is totally extinguished and the contents are sufficiently cool he will give the signals for water off and make up.

Emergency Response Considerations

Self-Contained Breathing Apparatus

Drager PA93

Hazardous Chemicals

Drager BG174

Drager BG4

Gases

Fire

First Aid

Rope Rescue

Case Study - Pasminco Fire

Major Disaster Case Studies

Glossary

Summary of the Principles of Rescue Work

Guidelines for the Frequency of Practice Sessions


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