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1) CHEMICAL ENERGY

Primary heat source in combustion.
Subtypes:
- Heat of Combustion (calorific or fuel value): quantity of heat released during complete oxidation of a fuel to water and carbon dioxide.
- Spontaneous Heating: gradual heat buildup from slow oxidation leading to ignition.
- Heat of Solution: heat released when a substance dissolves.
- Heat of Decomposition: heat released during decomposition requiring heat input for formation.

2) ELECTRICAL ENERGY

Can generate high enough temperatures to ignite nearby combustibles.
Produced when current flows through a conductor or a spark jumps an air gap.
Types:
- Resistive heating: rate of heat generation proportional to resistance and square of current.
- Lighting: heat from lightning; static electricity (electrical discharge on contact and separation).
- Heat from Arcing: caused by interruption of circuit or loose connections.
- Inductive Heating: heating increases with frequency.

3) NUCLEAR ENERGY

Generated by fission or fusion; releases heat, radiation, pressure.
Nuclear Fusion – two light nuclei combine to form heavier nucleus with emission of particles or gamma rays.
Nuclear Fission – neutron bombardment causing nucleus split (e.g., uranium, thorium).

4) MECHANICAL ENERGY

A fire extinguisher is a mechanical device usually made of metal containing chemicals, fluids, or gases to stop fires.
Portable device used to extinguish fires of limited size.

a. Extinguishment by Temperature Reduction (Cooling)

Use water to cool the fuel, reducing temperature to below the point where vapors form enough to sustain ignition.

b. Extinguishment by Fuel Removal (Fuel Depletion)

Eliminate fuel source or supply; stop flow of liquid fuel; prevent production of flammable gas; remove solid fuel along path; allow burn to complete if fuel is consumed.

c. Extinguishment by Oxygen Dilution (Oxygen Exclusion)

Reduce oxygen concentration at the burning area; introduce inert gases; separate oxygen from fuel.

d. Extinguishment by Chemical Inhibition

Effective mainly for burning gas and liquid fuels; cannot stop smoldering combustion; disrupts the chemical chain reaction.

Clean agent fire suppression systems can stop fires with no cleanup and no risk to people or environment, protecting precision gear, data centers, electrical cabinets, etc.
Choice of agent depends on fire type; some agents more effective for specific classes.

Do not fight unless trained and confident of the extinguisher type; if unsure, evacuate and call fire department.

Water Extinguisher – for Class A and B (not for Class C).
Liquefied Gas Extinguisher – CO2-based; for Class A, B, and C.
Dry Chemical Extinguisher – powder for all classes.
Foam Extinguisher – foam with sodium bicarbonate and aluminum sulfate to form CO₂ foam.
Soda-Acid Extinguisher – sodium bicarbonate with a sulfuric acid component activated by inversion.
Vaporizing Liquid Extinguisher – non-conducting liquid (e.g., chlorinated solvents) for liquids and electrical fires.
Carbon Dioxide Extinguisher – effective for liquids and live electrical fires; mainly for Class C.
Wet Chemical Extinguisher – specialized for commercial cooking fires.

Range: varies by class; effectiveness and safety considerations (e.g., CO₂ can cause breathing difficulties in enclosed spaces; powders may leave residue).

Fire Hydrant (also called fireplug, firecock, or Johnny Pump): a connection point to access a water supply for firefighting; part of active fire protection.
Underground hydrants have existed since at least the 18th century; above-ground pillar hydrants were invented in the 19th century.
Main function: provide rapid access to water for firefighters; ensures high-pressure water delivery.
Water Hammer: a pressure surge when a fluid in motion is forced to stop or change direction suddenly.

Dry Fire Hydrant – used where temperatures fall below freezing; primary valve is below the frost line; hydrant is kept dry when not in use to avoid freezing; supply must be activated.
Wet Fire Hydrant – used where temperatures do not fall below freezing; primary valve at the bottom; barrel remains full of water.

Assess the situation: determine fire size/location/intensity; ensure safety; identify the nearest hydrant and coordinate with team and incident command.
Gather necessary equipment: hydrant wrench, hose, nozzle, etc.; ensure equipment is in good condition.
Remove obstructions from access to hydrant (snow, ice, vehicles, debris).
Open the hydrant: loosen and remove the cap with a hydrant wrench; stay clear of residual pressure; inspect threads/connections before attaching hose.
Attach the hose: connect one end to hydrant outlet; ensure threads match; tighten; inspect hose for kinks or damage.
Control water flow: slowly open hydrant valve; monitor pressure gauge; adjust as needed for required flow/pressure.
Direct water stream: gradually open valve; maintain stable pressure; adjust as needed.
Monitor water supply: assign a firefighter to monitor supply/pressure; report fluctuations to incident commander; adjust hydrant valve as needed.
Coordinate with firefighters: maintain communication to align with incident strategy.
Close the hydrant: when fire is out or under control, tighten the valve clockwise; replace cap; inspect hydrant area before ending.