fire fighting

Definition of Fire:

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition. The flame is the visible portion of the fire.

Types of Fire:

There are six types of Fire.

"A" Class Fire:  Solid Fire:

Class A fires consist of ordinary combustibles such as wood, paper, fabric, and most kinds of trash.

"B" Class Fie:  Liquid Fire:
These are fires whose fuel is flammable or combustible liquid.  Such as gasoline,

A solid stream of water should never be used to extinguish this type because it can cause the fuel to scatter, spreading the flames. The most effective way to extinguish a liquid fire is by inhibiting the chemical chain reaction of the fire, which is done by dry chemical and Halo extinguishing agents, although smothering with CO₂ Chemicals such as FM-200 are now the recommended halogenated suppressant.

PROPERTIES OF SOME COMMON LIQUID FUELS

Name	F.PoC	I.T  C	L/L	U/L	S.G	V.D
Ethyl Alcohol	13	423	4.3	19.0	0.8	1.6
Gasoline	-43	2 80 to 456	1.4	7.4	0.8	3to4
Kerosene	38	229	0.7	5.0	1.0	-
Petroleum Ether benzene	-46	22 8	1.1	5.9	0.6	2.5

"C" Class Fire:  Gas Fire:

Burning gases are separately designated "Class C". These fires follow the same basic fire tetrahedron (heat, fuel, oxygen, chemical reaction) as ordinary combustible fires,

"D" Class Fire:  Metal Fire:

Class D fires consist of combustible metals such as magnesium, potassium, titanium, and zirconium.

"E" Class Fire:  Electrical Fire:

Electrical fires are fires involving potentially energized electrical equipment.  This sort of fire may be caused by short-circuiting machinery or overloaded electrical cables.

These fires can be a severe hazard to firefighters using water or other conductive agents, as electricity may be conducted from the fire, through water, to the firefighter's body, and then earth. Electrical shock have caused many firefighter deaths.

"F" or "K" Fire: Kitchen Fire:

Class K fires involve unsaturated cooking oils in well-insulated cooking appliances located in commercial kitchens.

Fire Extinguisher

A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations.

It is not intended for use on an out-of-control fire.

Typesof Fire Extinguishers:

Water Type,        Foam Type,        Dry Chemical,    Wet Chemical,

Water Mist,         Dry Powder,       Clean Agent,       Cartridge Operated Dry Chemical

PRODUCTS OF FIRE & EFFECTS ON LIFE SAFETY

Generally there are two types of products liberated in the process of combustion

v    Thermal products (Heat  &  Flame)

v    Non –thermal products ( Smoke & Toxic gases   

Toxic Gases  

v           CO₂, CO,SO₂,H₂S,HCN ,NH₃ ,HCL, NO₂

SMOKE         

           Visible smoke is composed of unburned particles, dust and liquid droplets.

Effects

¨     Suffocation

¨    Visibility is affected.

¨    Creates irritation in the respiratory tract.

EFFECTS OF TOXIC GASES

Carbon-Di-Oxide (CO₂).

The main effect of CO2 is    suffocation but at different concentration it has       different effects as shown in the table:-

Amount of CO2 in air	Effects
0.5%	No symptoms and no permanent danger.
2.0%	Increase the breathing rate by 50%
3.0%	Increase the breathing rate by 100%
5.0	Vomiting, dizziness, breathing difficulties after 30 minutes.
8.10%	Vomiting, headache, dizziness, unconsciousness and death after some time.

                    

CARBON-MONO-OXIDE (CO)

When (co) is inhaled, it combines with hemoglobin; and car boxy hemoglobin is formed. Car boxy hemoglobin has different effects as shown in the table:-

Amount of Car boxy

Hemoglobin in blood	Effects
10	Possible shortness of breathe
20-30	Shortness of breath, headache.
30-50	Severe headache, mental confusion, dizziness, fatigue
50-70	Unconsciousness, death and respiratory failure if exposure is continued.
70 & above	Rapidly fatal.

SULPHER-DI-OXIDE (SO₂)

          Its source materials are rubber ,wood , sulfuric acid and pesticides etc. Its toxicological effects are eyes and lungs irritation.

HYDROGEN SUPHIDE (H₂S)

          Its source materials are leather, wood and other materials containing Sulpher. Its lethal concentration is 20 PPM. It is a nerve agent and creates paralysis.

AMMONIA (NH₃)

                   When wool, silk and melamine are involved in fires then (NH₃) is produced. It is soluble in water and      its main effect is irritation in eyes. It is fatal if exposure is longer.

HYDROGEN CHLORIDE (HCl)

          Its source materials are plastics i.e. PVC and ploy urethane. At low concentration causing coughing, choking and irritation in eyes.

          At high concentration can damage the upper respiratory tract, causing asphyxiation or death.

NITROGEN DIOXIDE (NO₂ )

                   Source materials are fabrics, cellulose acetate and all plastics containing Nitrogen. Its main effect is Asphyxiation and longer exposure can prove fatal.

HEAT

   Effects of heat

Ø           It declines blood pressure.

Ø           By inhalation of hot air fluid may build up in lungs.

Ø           It can cause burns & scalds

Ø           It can cause hypothermia