Fire Safety & Prevention in the Workplace

Workplace fires cause approximately 200 deaths, 5,000 injuries, and $2.5 billion in property damage every year in the United States. OSHA requires employers to have fire prevention plans (29 CFR 1910.39) and emergency action plans (29 CFR 1910.38), and mandates specific requirements for fire protection equipment and systems (29 CFR 1910 Subpart L). Every worker should understand how fires start, how to prevent them, how to use fire extinguishers, and how to evacuate safely when necessary.

The Science of Fire

The Fire Triangle

A fire needs three elements to ignite and sustain combustion:

• Heat - An ignition source: sparks, open flames, hot surfaces, electrical arcs, friction, chemical reactions
• Fuel - Any combustible material: wood, paper, flammable liquids, gases, metals, dust
• Oxygen - Normal air (20.9% O2) is sufficient. Some materials (oxidizers) supply their own oxygen.

Remove any one of these three elements and the fire goes out. This principle guides both fire prevention and fire suppression.

The Fire Tetrahedron

Modern fire science adds a fourth element: the chemical chain reaction. In a sustained fire, the combustion reaction produces free radicals that continue the reaction cycle. Certain extinguishing agents (dry chemical, halon alternatives) interrupt this chain reaction to suppress the fire. This is why a dry chemical extinguisher works even though it does not cool the fire or remove the fuel.

Stages of Fire Development

Understanding how fires develop helps you respond appropriately:

Stage 1: Incipient (Ignition)

• Fire begins at the ignition point
• Small flames, minimal smoke and heat
• This is when a portable fire extinguisher is effective
• The fire can typically be extinguished in the first 60-90 seconds

Stage 2: Growth

• Fire spreads to adjacent fuels
• Room temperature increases rapidly
• Smoke production increases
• Evacuation should be underway

Stage 3: Flashover

• All combustible materials in the room reach their ignition temperature simultaneously
• The room transitions from a fire in a room to a room on fire
• Temperatures exceed 1,000 degrees F at the ceiling
• Survival inside the room at flashover is unlikely

Stage 4: Fully Developed

• Maximum heat release rate
• All available fuel is burning
• Structural collapse becomes a concern
• This is when buildings fail

Stage 5: Decay

• Available fuel is consumed
• Temperatures begin to decrease
• Danger persists: hot embers, structural instability, toxic gases

Common Workplace Fire Hazards

Electrical Hazards

Electrical fires are the leading cause of workplace fires in many industries.

• Overloaded circuits - Drawing more current than the wiring can handle causes overheating
• Damaged cords and plugs - Exposed conductors can arc and ignite nearby materials
• Improper wiring - Extension cords used as permanent wiring, undersized conductors
• Loose connections - Electrical resistance at loose connections generates heat
• Space heaters - Unauthorized or improperly placed space heaters cause numerous fires each year

Prevention: Inspect all electrical equipment regularly. Never use damaged cords. Do not overload circuits or daisy-chain power strips. Space heaters must be UL listed, placed on flat surfaces, kept 3 feet from combustibles, and turned off when unattended.

Flammable Liquids and Gases

• Flash point is the minimum temperature at which a liquid produces enough vapor to ignite. Class I flammable liquids have flash points below 100 degrees F (gasoline: -45 degrees F, acetone: -4 degrees F).
• Vapors from flammable liquids are typically heavier than air and travel along the ground to ignition sources.
• Flammable gas leaks (propane, natural gas, hydrogen) create explosive atmospheres in enclosed spaces.

Prevention: Store in approved flammable storage cabinets. Use only in well-ventilated areas. Keep ignition sources (flames, sparks, hot surfaces, static) at least 50 feet away. Ground and bond containers during transfer. Keep containers closed when not in use.

Hot Work

Welding, cutting, brazing, grinding, and any operation that produces sparks or open flames.

• Sparks from grinding and welding can travel up to 35 feet horizontally and much farther vertically
• Hot metal slag can smolder for hours before igniting combustible material

Prevention: Follow your facility's hot work permit program. Clear combustible materials at least 35 feet from the work area, or cover them with fire-resistant blankets. Assign a fire watch during and for at least 30 minutes (60 minutes recommended) after hot work. The fire watch must have a fire extinguisher and the authority to stop work. OSHA Standard 1910.252(a) covers fire prevention for welding and cutting.

Combustible Dust

Fine particles of wood, metal, grain, sugar, plastic, and many other materials can form explosive dust clouds when suspended in air. Five conditions are required for a dust explosion (the "Dust Explosion Pentagon"):

1. Combustible dust (fuel)
2. Dispersion in air (dust cloud)
3. Confinement (enclosed space)
4. Ignition source
5. Oxygen

Prevention: Regular housekeeping to prevent dust accumulation. Use approved dust collection systems. Do not use compressed air to blow dust (this creates a suspended cloud). Maintain electrical equipment to prevent ignition sources. Follow NFPA 652 (Fundamentals of Combustible Dust) requirements.

Real Incident: Imperial Sugar Company (2008) - Accumulated sugar dust in an enclosed conveyor area ignited, creating an explosion that propagated through dust-laden areas of the refinery. 14 workers were killed and 38 were injured. The root cause was decades of accumulated combustible dust with inadequate housekeeping and dust collection. This incident led to significantly increased OSHA enforcement of combustible dust hazards.

Smoking and Ignition Sources

• Cigarettes burn at approximately 1,100 degrees F and can ignite paper, dry grass, and many other materials
• Lighters and matches are open flame sources
• Unauthorized smoking in non-designated areas is a common fire cause

Prevention: Enforce designated smoking areas located away from combustible storage. Provide proper cigarette disposal receptacles. Prohibit smoking near flammable liquid storage, fueling areas, and oxygen-enriched environments.

Fire Extinguisher Classes and Agents

Classes of Fire

Class A - Ordinary Combustibles

• Wood, paper, cloth, rubber, plastics, and trash
• Extinguishing agents: Water, foam, dry chemical (ABC), wet chemical
• Water cools the fuel below its ignition temperature

Class B - Flammable Liquids

• Gasoline, oil, grease, solvents, paints, lacquers, and flammable gases
• Extinguishing agents: CO2, dry chemical (BC or ABC), foam, clean agents
• Never use water on a Class B fire - water can spread burning liquid and cause a violent steam explosion in grease fires

Class C - Energized Electrical Equipment

• Fires involving equipment that is plugged in and energized
• Extinguishing agents: CO2, dry chemical, clean agents
• Never use water or foam on a Class C fire - electrical conductivity creates electrocution hazard
• Once equipment is de-energized, the fire becomes Class A or B and can be fought accordingly

Class D - Combustible Metals

• Magnesium, titanium, sodium, lithium, potassium, zirconium, and metal dusts
• Extinguishing agents: Special dry powder agents (sodium chloride, copper powder)
• Never use water on a Class D fire - many combustible metals react violently with water, producing hydrogen gas and intensifying the fire
• Class D fires require specialized extinguishers specifically rated for the metal involved

Class K - Cooking Oils and Fats

• Commercial cooking equipment (deep fryers, griddles, woks)
• Extinguishing agent: Wet chemical (potassium acetate solution)
• The wet chemical creates a soapy foam blanket (saponification) that cools and smothers the fire
• Commercial kitchens must have Class K extinguishers and automatic suppression systems

Common Extinguisher Types

Type	Classes	How It Works	Range	Duration
Water	A only	Cools fuel	30-40 ft	60 sec
ABC Dry Chemical	A, B, C	Interrupts chain reaction, smothers	10-20 ft	10-25 sec
BC Dry Chemical	B, C	Interrupts chain reaction	10-20 ft	10-25 sec
CO2	B, C	Displaces oxygen, cools slightly	3-8 ft	8-30 sec
Clean Agent (Halotron)	A, B, C	Interrupts chain reaction	6-12 ft	10-15 sec
Wet Chemical	A, K	Saponification, cooling	10-12 ft	30-40 sec
Class D Dry Powder	D only	Smothers, absorbs heat	Apply gently	Varies

The PASS Method

If you decide to fight a small fire with an extinguisher, use the PASS technique:

1. P - Pull the pin. This breaks the tamper seal and unlocks the operating lever. Hold the extinguisher with the nozzle pointing away from you.
2. A - Aim low. Point the nozzle, hose, or horn at the BASE of the fire, not at the flames. Hitting the flames does nothing - you must attack the fuel source.
3. S - Squeeze the lever slowly and evenly. This releases the extinguishing agent.
4. S - Sweep from side to side at the base of the fire. Keep the extinguisher aimed at the base and move from one side to the other until the fire appears to be out.

After the fire appears extinguished, watch for re-ignition. Back away while facing the fire. Do not turn your back on it.

The Decision to Fight or Flee

Fight the fire ONLY if ALL of these conditions are true:

• The fire is small and contained (roughly the size of a small trash can or smaller)
• You have the correct type and size of extinguisher
• You have a clear escape route behind you
• The room is not filling with smoke
• You have been trained to use the extinguisher
• You have already sounded the alarm or had someone else call for help
• Your instincts tell you it is safe to attempt

Evacuate IMMEDIATELY if ANY of these conditions exist:

• The fire is larger than a small trash can
• The fire is spreading rapidly
• Smoke is filling the room or blocking your view
• You do not have the correct extinguisher type
• You do not know what is burning
• You do not have a clear escape route
• The fire involves hazardous materials or explosives
• Your extinguisher empties and the fire is not out
• You have any doubt about your ability to fight the fire safely

When in doubt, get out. Your life is worth more than any property.

Fire Extinguisher Maintenance (29 CFR 1910.157)

OSHA requires:

• Monthly visual inspections: Verify the extinguisher is in its designated location, accessible, visible (not blocked), and that the pressure gauge is in the green zone. Check for physical damage, corrosion, and leakage. Verify the pin and tamper seal are intact. Document each inspection.
• Annual maintenance: A trained professional inspects each extinguisher according to NFPA 10. This includes checking the agent, testing the hose and nozzle, weighing CO2 extinguishers, and verifying all components.
• 6-year maintenance: Stored pressure extinguishers (ABC dry chemical) must be emptied, internally examined, recharged, and the maintenance recorded on a tag or label.
• 12-year hydrostatic test: The shell must be hydrostatically tested to verify structural integrity.

Placement Requirements

• Maximum travel distance to an extinguisher: 75 feet for Class A hazards, 50 feet for Class B hazards
• Mounting height: handle no more than 5 feet above the floor for extinguishers over 40 lbs, no more than 3.5 feet for lighter units
• Must not be obstructed or hidden from view
• Extinguishers must be appropriate for the hazards in the area

Evacuation Procedures

Emergency Action Plan Requirements (29 CFR 1910.38)

Every workplace must have a written emergency action plan that includes:

• Procedures for reporting a fire or other emergency
• Evacuation procedures and emergency escape route assignments
• Procedures for employees who remain to operate critical plant operations before evacuating
• Procedures to account for all employees after evacuation
• Rescue and medical duties for designated employees
• Contact information for additional information or explanation

Your Personal Evacuation Knowledge

Before an emergency happens, know:

• At least two exits from your immediate work area
• The location of the nearest fire alarm pull station
• The location of the nearest fire extinguisher
• Your designated assembly point outside the building
• Who is responsible for headcount at your assembly point
• The location of people in your area who may need assistance (mobility limitations, hearing/vision impairment)

During an Evacuation

• Leave immediately when the alarm sounds. Do not finish your task, gather belongings, or investigate.
• Close doors behind you as you exit. A closed door can hold back fire and smoke for 20+ minutes.
• Feel doors before opening. If the door or handle is hot, do not open it. Use an alternate route.
• Stay low if smoke is present. Breathable air is closest to the floor. Crawl if necessary.
• Use stairs - never use elevators during a fire.
• Go to your assembly point and report to the person taking headcount.
• Do not re-enter the building until the fire department gives an all-clear.
• Report anyone missing to emergency responders immediately.

If Trapped

• Close the door and seal gaps with clothing or other available material
• Move to a window and signal for help
• Call 911 and tell them your exact location in the building
• Stay low to avoid smoke inhalation
• Do not break windows unless absolutely necessary (broken windows draw smoke and fire)

Fire Prevention Best Practices Checklist

• [ ] Electrical equipment inspected regularly, damaged cords replaced
• [ ] Flammable liquids stored in approved cabinets, away from ignition sources
• [ ] Combustible materials kept away from heat sources (3-foot minimum clearance)
• [ ] Housekeeping maintained - combustible waste removed regularly
• [ ] Hot work permits issued and fire watch assigned for welding/cutting/grinding
• [ ] Combustible dust accumulations cleaned up, dust collection systems maintained
• [ ] Smoking restricted to designated areas with proper disposal
• [ ] Fire extinguishers inspected monthly and serviced annually
• [ ] Fire exits and routes clearly marked, illuminated, and unobstructed
• [ ] Sprinkler heads unobstructed (18 inches clearance minimum)
• [ ] Emergency action plan reviewed and practiced (annual drills)
• [ ] Fire alarm and detection systems tested per manufacturer's schedule
• [ ] Cooking equipment equipped with Class K extinguisher and auto-suppression
• [ ] All workers trained on fire prevention, extinguisher use, and evacuation

Key Takeaways

• Fire needs heat, fuel, and oxygen. Remove any one to prevent or extinguish a fire.
• Know the fire extinguisher classes: A (ordinary combustibles), B (flammable liquids), C (electrical), D (metals), K (cooking oils). Using the wrong type can make a fire worse or endanger you.
• Use the PASS method (Pull, Aim, Squeeze, Sweep) and only fight fires that are small, contained, and that you have the right equipment for. When in doubt, get out.
• Combustible dust explosions are preventable with good housekeeping and dust collection. Accumulated dust is fuel waiting for an ignition source.
• Know your evacuation routes, assembly point, and the location of fire extinguishers and alarm pull stations before an emergency happens.
• Close doors when evacuating. Never use elevators. Stay low in smoke. Account for all personnel at the assembly point.
• Hot work (welding, cutting, grinding) requires a permit, a clear area, and a fire watch with an extinguisher during work and for at least 30 minutes after.