NATIONAL UNIVERSITY OF SCIENCE AND TECHNOLOGY

FACULTY OF APPLIED SCIENCES

DEPARTMENT OF ENVIRONMENTAL SCIENCE AND HEALTH

PROGRAMME: Bachelor of Science Honors Degree in Environmental Science and Health

NAME: STEWART TATENDA SANHEWE

SUPERVISOR: Missrs. A. Mutsikira

ASSIGNMENT TOPIC: Define Fire, Fireguard and describe the

types of fire extinguishers and the fire

colour coding system

DUE DATE: 21/11/23

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 INTRODUCTION
Fire safety is a critical concern in both residential and commercial settings with fire safety dating
back as the 17th century with the Great fire of London, a prime factor that catalyzed the birth of
firefighting which matured into fire safety with the progression of the times. With the Great
London and the Great New York fires of 1666 and 1835 and more that occurred it became clear
the unpredictability and devastation with extensive damage to property and significant risks to
human life due to fire. By 1723 fire extinguishers were developed by a chemist (Ambrose
Godfrey) which serve as indispensable tools for preventing and suppressing fires, playing a
crucial role in protecting lives and property. In this work I am going to describe the type of fire
extinguishers and their subsequent fire colour coding. To ensure that fire extinguishers are used
appropriately, a colour coding system has been established, providing quick identification of the
type of fire for which a particular extinguisher is suitable. This colour-coding system helps
individuals select the correct fire extinguisher based on the fire class, allowing for a rapid and
effective response to different types of fires. Knowledge of fire extinguisher colour and types is
paramount for everyone’s safety as in emergency situations, every second counts, and being able
to identify the appropriate fire extinguisher quickly can make a significant difference in
containing a fire before it escalates which empowers one’s self to take immediate action,
potentially saving lives and minimizing property damage. They are the best method of
extinguishing a fire as according to communication between the three pillars that give rise to a
fire has to be eliminated.

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DEFINITIONS
According to dictionary.com, fire is a ‘state, process, or instance of combustion in which fuel or
other material is ignited and combined with oxygen, giving off light, heat, and flame’, it is a
rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion,
releasing heat, light, and various reaction products
According to EMA, a “standard fireguard is one which measures at least 9metres wide on either
side of a boundary line/fence. It then follows that between two properties, the fireguard becomes
at least 18metres wide. Internal fireguards of at least 4; 5 meters should be constructed in
addition to the existing pathways and roads to ensure extra- protection of properties and other
valuables. The width of the fireguards should be increased if the area is surrounded by tall grass”

TYPES OF FIRE EXTINGUISHERS

Fire extinguisher identification comes in two camps of classification. The first classification of
fire extinguishers is according to their fire retardant/extinguishing agent composition which are:

1. Water (Water spray, water mist)

2. Dry powder

3. Foam

4. Carbon dioxide (CO2)

5. Wet chemical

The second classification of fire extinguishers is according to the storage mechanism of the fire

retardant/extinguishing agent:

1. Cartridge operated

2. Stored pressure operated

First Classification

Water
Water fire extinguishers work by removing the heat source from the fire. The cooling action of
the water slows down the burning until the flames are extinguished. They are most commonly
used for Class A fires. It is however not used on electrical equipment, kitchen fires or fires

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involving flammable gas and liquids due to its conductivity and the ability to act as a solvent,
however for some, additives can be employed to the water to prevent conductivity and they have
to be di-electrically tested before issuance and use. A water mist extinguisher can, however, be
used on electrical and hot fat fires as fine water particles are sprayed which do not conduct
electricity at regular commercial voltage levels and puddles are also not formed.

Dry powder
Dry powder extinguishers put out fire by coating the fuel with a thin layer of dust, separating the

fuel from the oxygen in the air. The powder also works to interrupt the chemical reaction of fire,

so these extinguishers are extremely effective at putting out fire. There are just two types of dry

powder fire extinguishers available: standard and specialist. Standard dry powder extinguishers

can extinguish almost any type of fire. Specialist dry powder extinguishers are for certain types

of metal fires. However, because of the dispersal of powder, it’s important not to use them in

enclosed spaces.

Dry powder extinguishers are also known as:

 ABC fire extinguishers

 Multi-purpose fire extinguishers

 Dry chemical fire extinguishers

Foam
They are non-toxic and extinguish the fire by forming a blanket on the surface of the burning

hazard, which both cools and smothers the fire by removing the oxygen. Removing the heat and

oxygen from the fire also helps to prevent re-ignition.

The types of foam extinguishers include:

Aqueous Film Forming Foam

AFFF extinguishes flammable liquid fires by forming an aqueous film on the surface of the

liquid solutions. This type of extinguisher is particularly useful for a fire that may not be

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affected by water. The AFFF can quickly bring a fire under control. These foam solutions can

be applied to a fire using either aspirating or non-aspirating devices.

Film Forming Fluoroprotein

FFFP FOAM is appropriate to use for Class A and B fires. The Alcohol Resistant fire-fighting

agent is particularly effective on fires of Class B materials including: alcohols, polar solvents,

hydrocarbons and combinations such as gasohol. A unique benefit for the foam-extinguishing

agent is that it may be applied to a non-ignited Class B liquid spill to help seal the surface and

prevent a serious fire from occurring.

Carbon dioxide (CO2)

Carbon Dioxide extinguishers are filled with non-flammable carbon dioxide gas under extreme

pressure. The pressure in the cylinder is very high to the extent where bits of dry ice may shoot

out of the hard horn. Carbon dioxide extinguishes work by displacing oxygen, or taking away the

oxygen element of the fire triangle. The carbon dioxide is also very cold as it comes out of the

extinguisher, so it cools the fuel as well. CO2s may be ineffective at extinguishing Class A fires

because they may not be able to displace enough oxygen to successfully put the fire out. Class A

materials may also smolder and re-ignite.

Wet chemical
Chemical fire extinguisher can consist of a few different chemical combinations: water and
potassium acetate, potassium carbonate, and potassium citrate. These ingredients help to combat
the high temperatures of cooking oils by quickly reducing heat and sealing (also cool on contact)
the oil within the soapy solution to prevent the oil or grease from reigniting. Usually have a long
hose to allow the user to stand back at a safe distance from the fire.

Second classification

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Cartridge Operated
Designed for rugged industrial use, cartridge operated extinguishers are different from stored
pressure extinguishers based on where the propellant for the extinguishing agent is stored. In
cartridge operated units, the dry chemical is stored in the non-pressurized cylinder while the
propellant; either “dry air” or nitrogen is stored in a separate cartridge located on the side of the
unit. Most cartridge operated extinguishers have the fire-retardant composition come in powder
or dry chemical form. The general morphology is composed of a metal diffusor tube with lock
nut which provides durability; an aluminium siphon tube to withstand sudden impact and tough
industrial handling; a pressure release device on the valve which limits pressure within the
cylinder to the specified value and prevents accidents due to overpressure in the extinguisher;
vertical slots on mounting threads which provide venting passage for
residual pressure reducing accidental risks while servicing and maintenance.

Cartridge operated units are preferred in the construction and heavy equipment industries for the
following reasons:

 Durable and withstand heavy industrial construction activity

 simple design reduces possibility of failure
 better suited for harsh environments
 Cartridge extinguishers can be opened at every inspection hence problems can be
detected early and remedied quickly

Industrial Dry Chemical Fire Extinguisher

It has a specialized coating and paint on the cylinder makes this unit a better choice for corrosive
and more industrial environments. They are rechargeable and manufactured with high quality,
durable materials. The 6L fat fire extinguisher extinguishes cooking oil fires in industrial
kitchens and canteens. It can be integrated into an automated system in open kitchens where
automatic equipment is required.

Stored Pressure

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Stored pressure fire extinguishers are the most common type being used recently as cartridges
are being phased out. In these units, the propellant is stored in the same cylinder as the retardant
agent itself. The different agents used in the fire extinguisher require different propellants. Dry
chemical extinguishers typically use nitrogen or dry air as a means of propelling the agent onto
the fire. Water and foam extinguishers typically use air, the propellant is contained under
pressure ranging from 5 to 15 bar. Discharge is initiated by either opening the valve or by
piercing a sealing disc. Upon discharge, the compressed gas expands to fill the extinguisher body
and expel the extinguishing medium.

These units are now mostly preferred as:

 Stored pressure units usually feature a tell-tale gauge or pressure disc on their operating
assembly or body to indicate the pressure held in the container.
 Operation is usually marginally quicker due to simplicity.
 Better rating to weight ratio meaning it will be lighter
 Units are much more cost effective in terms of maintenance/servicing due to the
minimum amount of work required.

The most common types of stored pressure extinguishers include:

1. ABC Dry Chemical – Reliable Fire & Security recommends ABC dry chemical
extinguishers that can be used for many common fires.
2. BC Dry Chemical– Suitable for use on flammable liquids and energized electrical
equipment.
3. Special Application Extinguishers

 K-Class and F-Class extinguishers (for restaurant kitchen hazards)

 Class D agents (for combustible metals such as magnesium, sodium,
potassium, lithium and uranium)
 Foam which is recommended for use on Class A combustibles and Class B
flammable liquids.

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 4. Clean Agent extinguishers contain various environmentally friendly, non-residue forming
chemicals well-suited for flammable liquids and energized electrical equipment.
5. Carbon Dioxide (CO2) Extinguishers are used for class B flammable liquids fires as well
as Class C Electrical fires.
6. Pressurized Water – used for Class A fires only.
7. Water Mist is a useful extinguisher for Class A fires and where a potential Class C
(electrical) hazard exists.

FIRE EXTINGUISHER COLOURS

Fire extinguisher colour come in mainly 5 colour coding which are:

1. Red – Water (both spray and mist)

2. Blue – Dry powder

3. Cream – Foam

4. Black – Carbon dioxide (CO2)

5. Yellow – Wet chemical

Colour coding is a crucial criterion for fire extinguishers as it assists in easily determining the
type of fire extinguisher according to the class of fire it is able to effectively distinguish which
assists during a fire emergency response as a need to read the type of fire extinguisher, it is and
which class it effectively works against, is eliminated reducing reaction time for a response.
Generally all fire extinguishers have a red or chrome body, each type is identified using

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individual fire extinguisher colour codes shown on a band at the top of the extinguisher. Up until
1997, the body colour of the fire extinguisher was the only identification factor i.e. carbon
dioxide extinguishers were completely black, and dry powder extinguishers were blue. This all
changed, however, to fall in line with British Standard and European Standard BS EN3, with the
red colouringcoloring making it easier to locate a fire extinguisher when in a smoke-filled or
dark environment. Chrome colouredcolored extinguishers, whilst not quite fitting with the
visibility concept, are still tested against BS EN3 standard however it is recommended they are
used alongside more
prominent fire extinguisher signs so that they are more obviously visible.

COLOUR TYPE CLASS USE ON NOTES

OF FIRE

Red Water A Organic solids e.g. Not suitable for

paper, wood, straw, electrical or deep fat
plastics, coal, soft fires
furnishings

Blue Dry powder A, B, C, D Organic solids plus Not suitable for

flammable liquids electrical fires over
Electrical
e.g. petrol, oil, 1,000 volts
solvents, paraffin,
tars; flammable
liquids e.g. propane,
butane, methane;
metals and swarf;
electrical fires

Black Carbon B, C Flammable liquids, Suitable for high

dioxide electrical electrical fires and low voltage

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 electrical fires

Yellow Wet chemical A, F Organic solids, Suitable for use at

cooking oils and fats very high
temperatures

Cream Foam A, B Organic solids, Not suitable for

flammable liquids domestic fires

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Mainly the fire extinguishers come in the described types however there are new types being
introduced and specialized types specific to certain environments or situations. These are the
following:

SMALL FIRE EXTINGUISHERS

Small fire extinguishers are designed for compact, enclosed spaces, where there is limited
storage. They are also lighter and easier to handle. Mini fire extinguishers can be dry powder or
foam. They are easy-to-operate and alsoand environmentally friendly aerosols are used.

REFURBISHED FIRE EXTINGUISHERS

They are usually only available in carbon dioxide and sometimes dry powder.

MAINTENANCE-FREE FIRE EXTINGUISHERS

P50 maintenance-free fire extinguishers are designed to avoid internal corrosion by containing
the extinguishing chemicals within a multi-layered composite container. This means they don’t
need regular servicing. They are constructed with additional security features to ensure it remains
possible to gauge the correct pressure and check the safe status of the extinguisher. Visual
inspections are still required, the hose must be checked for obstruction and the pressure indicator
read regularly.

CONCLUSION
Just as how fire in its different states/forms is a crucial resource in the day to day activities of
human beings and also due to the conditions for a chain reaction to occur that leads to a fire, are
found almost everywhere and around human beings, it can also be a devastating and destructive
force when given the opportune time and chance for the conditions/three pillars to interact.
Hence fire safety is a crucial knowledge and skill necessary to possess by human beings of all
social standings as it enables one to fight against small fires or the onset stages of fire production
which can save lives and also reduce damage to property or implications to health or wellbeing.
The wide range of types of fire extinguishers ensures that fire which has numerous sources of
fuel can be adequately catered for and also that each type of premises e.g. Laboratory, vehicles,
offices, construction sites, etc. are also accommodated ensuring fire safety has a wide reach of
area/situation of effectiveness.

COMMENT(S):

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  A well-articulated assignment, it is well detailed and chronological.
 Ensure that you understand the contents and the applicability of these
context in real life scenarios.


REFERENCES

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https://www.sc.edu/ehs/training/Fire/05_co2.htm#:~:text=Carbon%20Dioxide
%20extinguishers%20are%20filled.

Reliable Fire & Security. (n.d.). Foam Extinguishers - Reliable Fire Equipment
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Installation and Awareness of Fire Extinguishers and Awareness of Fire
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Britain, G. (1974). Manual of Firemanship.

‌Fire (n.d.). Guide to the Servicing of Portable Fire Extinguishers.

‌Ridley, J.R. (2014). Safety at Work. Elsevier.

‌British Standards Institution (2020). BS EN 3-8. Portable Fire Extinguishers.

‌www.dictionary.com. (2019). Definition of fire | Dictionary.com. [Online] Available
at: https://www.dictionary.com/browse/fire.

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