2.5 Fire Safety, Prevention, and Emergency Response

2.5 Fire Safety, Prevention, and Emergency Response

Chemistry of Fire: Triangle vs. Tetrahedron

To effectively prevent and extinguish fires, a Safety Officer 2 must understand the chemical mechanisms of combustion. Historically, fire was explained using the Fire Triangle, which consists of three elements:

1. Fuel: Any combustible material (solid, liquid, or gas).
2. Oxygen: Ambient air containing at least 16% oxygen concentration (normal air contains ~21% $O_2$).
3. Heat: Thermal energy sufficient to raise fuel to its ignition temperature.

Modern fire science expands this model into the Fire Tetrahedron, adding a crucial fourth element: the Uninhibited Chemical Chain Reaction.

                  [ OXYGEN ]
                    /    \
                   /      \
                  /  FIRE  \
                 /   TETRA  \
                /   HEDRON   \
   [ FUEL ] ---+--------------+--- [ HEAT ]
                \
                 \
       [ CHEMICAL CHAIN REACTION ]

Extinguishing Principle: Fire suppression works by removing one or more of the four sides of the tetrahedron:

• Remove Heat -> Cooling (e.g., applying water).
• Remove Oxygen -> Smothering (e.g., applying $CO_2$ or foam blanket).
• Remove Fuel -> Starvation (e.g., shutting off fuel valves).
• Interrupt Chain Reaction -> Chemical inhibition (e.g., applying Dry Chemical powders).

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Fire Classifications & Extinguishing Agents

Under Philippine OSH Standards (DOLE Rule 1940) and Republic Act No. 9514 (Fire Code of the Philippines), fires are categorized into five distinct classes based on fuel source:

1. Class A Fires (Ordinary Combustibles)

• Fuel Source: Wood, paper, cloth, rubber, plastics, trash.
• Extinguishing Agents: Water (cools), ABC Dry Chemical, Foam.
• Identification Symbol: Green Triangle with letter 'A'.

2. Class B Fires (Flammable Liquids & Gases)

• Fuel Source: Gasoline, diesel, kerosene, paint, oil-based solvents, methane, propane, LPG.
• Extinguishing Agents: Carbon Dioxide ($CO_2$), Foam (AFFF), ABC/BC Dry Chemical.
• CRITICAL EXAM WARNING: NEVER use water on Class B fires! Water is heavier than most flammable liquids; liquid fuel will float on top of water, spreading flaming liquid rapidly across the facility.
• Identification Symbol: Red Square with letter 'B'.

3. Class C Fires (Energized Electrical Equipment)

• Fuel Source: Live electrical wiring, circuit breakers, electric motors, transformers, appliances.
• Extinguishing Agents: Carbon Dioxide ($CO_2$), BC/ABC Dry Chemical (non-conductive agents).
• CRITICAL EXAM WARNING: NEVER use water or foam on live Class C fires! Water conducts electricity, causing immediate fatal electrocution to the operator. De-energizing the circuit reclassifies it to Class A or B.
• Identification Symbol: Blue Circle with letter 'C'.

4. Class D Fires (Combustible Metals)

• Fuel Source: Magnesium, titanium, sodium, potassium, zirconium, lithium.
• Extinguishing Agents: Special Class D Dry Powder (e.g., sodium chloride or graphite-based agents).
• CRITICAL EXAM WARNING: Water applied to burning magnesium causes a violent chemical reaction releasing hydrogen gas, resulting in severe explosions.
• Identification Symbol: Yellow 5-Point Star with letter 'D'.

5. Class K Fires (Commercial Kitchen Oils & Greases)

• Fuel Source: Vegetable oils, animal fats, lard, canola oil in deep fat fryers.
• Extinguishing Agents: Wet Chemical agents (potassium acetate/potassium carbonate solutions).
• Mechanism: Saponification—the wet chemical reacts with hot fat to form a thick soapy foam layer that smothers oxygen and cools oil below flash point.
• Identification Symbol: Black Hexagon with letter 'K'.

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Portable Fire Extinguisher Operation & Placement

The PASS Operating Method

When operating a portable fire extinguisher, personnel must follow the universal four-step PASS technique:

1. P - Pull: Pull the safety pin located at the top of the extinguisher handle, breaking the plastic tamper seal.
2. A - Aim: Aim the extinguisher nozzle or hose low, pointing directly at the base of the fire, not at the flames.
3. S - Squeeze: Squeeze operating handle or lever tightly to discharge extinguishing agent.
4. S - Sweep: Sweep nozzle side to side across the base of the fire until completely extinguished.

  [P]ull Pin ---> [A]im at Base ---> [S]queeze Lever ---> [S]weep Side-to-Side

DOLE Rule 1940 Extinguisher Placement Rules

• Maximum Travel Distance to Extinguisher:
  • Class A hazard areas: Maximum 15 meters (50 feet) travel distance.
  • Class B hazard areas: Maximum 10 meters (30 feet) travel distance.
• Mounting Height: Extinguishers weighing under 18 kg (40 lbs) must be mounted so top is no higher than 1.5 meters (5 feet) above floor. Extinguishers must never sit directly on floor.

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Emergency Preparedness & Evacuation Planning

Under DOLE Rule 1940 and RA 9514, the Safety Officer 2 is responsible for establishing an Emergency Preparedness and Response Program (EPRP):

1. Fire Brigade Organization: Establish a trained workplace Fire Brigade headed by a Fire Safety Inspector / SO2.
2. Means of Egress (Exits):
   • Every building must have at least two unblocked, remote emergency exits per floor.
   • Exit doors must swing outward in direction of travel and be equipped with panic hardware.
   • Exits must never be locked, bolted, or obstructed during working hours.
3. Emergency Lighting & Signs: Illuminated "EXIT" signs backed by emergency battery units providing at least 90 minutes of illumination during power failure.
4. Drills & Exercises: Mandatory conducting of workplace fire drills and earthquake evacuation drills at least twice per year, with complete documentation submitted to DOLE and Bureau of Fire Protection (BFP).