1. Flammability, Combustion, and Fire Protection

2. Objectives Know and understand: –Principles of combustible and flammable liquids, including limits, and classification –Basics of fire chemistry –Fire classes –How extinguishing agents work Be familiar with –Types of fire extinguishers –How to control flammable liquid hazards –Basic fire prevention and protection

3. Fire Hazards Annual $2.2 billion loss Over 300 workplace deaths Over 3% of workplace fatalities Fire losses can be catastrophic –Unlike other hazards, the event may not be self- limiting Fire hazards MUST be controlled to a low level of probability, as losses are so high

4. Flammability limits Lower explosive limit, LEL (also LFL) –The minimum concentration of vapor in air below which a spread of flame does not occur when the vapor is in contact with a source of ignition –Acetone LEL = 2.5% Upper explosive limit, UEL (also UFL) –The maximum concentration of vapor in air above which a spread of flame does not occur when the vapor is in contact with a source of ignition. –Acetone UEL = 12.8% Explosive range (also flammable range) –The spread between the LEL and UEL –Acetone explosive range = 2.5 - 12.8%

5. Concentration Explosive energy LEL UEL

6. Relationship between toxicity and flammability Toluene Example: TLV PEL IDLH LEL UEL 1 - 100 ppm 1000-5000 ppm 1-20 percent TLV=50 ppm, PEL = 200 ppm, IDLH = 500 ppm, LEL = 1.1%, UEL 7.1% O 2 deficient

7. Definitions Ignition temperature –The temperature at which ignition (production of flame) and burning will be continued after the source of ignition or the source of heat is removed Flash point –The lowest temperature at which enough vapor is given off near the surface of a liquid to produce a flammable mixture with air. Flammable liquid –Liquids with a flash point below 100 F Combustible liquid –Liquids with a flash point 100 F or greater

8. OSHA and NFPA Classification NFPAOSHAFlashpointBoiling point Flammable Liquids 4IA<73F< 100F 3IB<73F>100F 3IC>73 - <100F Combustible liquids 2II>100 - <140F 2IIIA>140 - <200F 1IIIB>200F Non- combustible 0

9. Fire Types Flame fire –Gases or vapors –High burning rate Surface fire –Burning rate may be slow Explosion –An event leading to a rapid increase of pressure

10. Explosions Deflagration –Combustion wave propagates at subsonic velocity Detonation –Combustion wave propagates at supersonic velocity Gas or vapor explosion –Combustion of pre-mixed gas or vapor Dust explosion –Finely divided solids, suspended in air

11. Explosions BLEVE –Boiling Liquid Expanding Vapor Explosion –Flash evaporation after vessel rupture –May not involve combustion

12. Chemistry of Fire Combustion –Rapid oxidation Combustion components –Oxygen Atmosphere (21%) Chemical oxidizers –Fuel Solids –Surface-to-mass ratio Gaseous Liquids (vapors) BGases

13. Chemistry of Fire Combustion components (cont.) –Heat Heat of combustion Other sources of heat: (ignition) –Chemical reactions Decay Slow oxidation –Electricity Arcing Resistance –Mechanical friction –Chemical Chain Reaction Propagated by free radicals

14. Products of combustion Heat Soot, smoke Carbon dioxide Carbon monoxide –Incomplete combustion Hydrogen cyanide Hydrogen sulfide Phosgene Acid Gases –Hydrogen Chloride –Sulfur dioxide Nitrogen oxides Ammonia Acrolein Metal Fumes

15. The Fire Triangle Four components: –Oxygen –Heat –Fuel –Reaction Removing any component stops the fire

16. Extinguishing a fire Cooling –Applying water Removing Fuel –Shut off supply to gas or liquid fires –Pump liquid from burning tanks Limiting oxygen –Mechanical smothering –Foam –Displace oxygen with inert gas Interrupt chain reaction –Capture free radicals using an extinguishing agent

17. Fire Classification Class A –Ordinary combustibles –Wood, paper, rubbish –Extinguish with water Class B –Flammable liquids –Water may aggravate a burning liquid fire –Extinguish with foam, chemical agents

18. Fire Classification Class C –Fires in electrical equipment –Use non-conductive extinguishing agent Class D –Combustible metal fires –Extinguish by smothering with dry powder –Water will cause burning metals to explode Special categories

19. Extinguishing agents Water –Removes heat from a fire –Streams, spray or fog –Best for Class A fires –Not for electrical or combustible metal fires Water mist may be used on electrical fires. These are special fire extinguishers, filled with distilled water, that produce a fine mist (no solid stream of water) Foam –Excludes oxygen from burning liquid fires –Aqueous Film Forming Foam (AFFF) –Fire can re-ignite if foam breaks down

20. Extinguishing agents Inert Gases –Displaces oxygen –Carbon dioxide, nitrogen Halogenated Hydrocarbons –Inhibit chain reactions –HALON (bromo-fluoro-chloro-hyrdrocarbons) –Carbon tetrachloride (historically) –Ozone depleting –New, more ozone-friendly agents are available

21. Extinguishing agents Dry Chemical –Inhibit chain reactions –Sodium or potassium bicarbonate –For Class B or C fires Multipurpose Dry Chemical –Monoammonium phosphate –For Class A, B, or C fires –Excludes oxygen by coating surfaces Dry Powder –Excludes oxygen from burning metal –Sodium chloride, graphite

22. Fire Extinguishers Water –For Class A fires –Minimum 2 1/2 gallons or 2A –"A" unit rating = 5 quart water or equivalent –Usually stored pressure type –Inverting soda-acid extinguisher are obsolete and dangerous Foam –For Class A or B –Stored pressure

23. Fire Extinguishers Dry Chemical –Class ABC or BC –"B" unit rating = 1 square foot flammable liquid fire –No rating for "C“ –Stored pressure or cartridge- operated

24. Fire Extinguishers Liquified Gas –CO 2, Class BC –HALON, Class ABC Dry powder –Class D (no rating) –Cartridge operated

25. OSHA Requirements for Fire Extinguishers Placement –Maximum 75 foot travel distance for "A" or "D“ –Maximum 50 foot travel distance for "B“ Inspection –Monthly visual –Annual maintenance –5-year hydrotest 12 yr. hydrotest for dry chemical or HALON (6 yr. recharge) Training and Education –For all workplaces with fire extinguishers

26. Using a Fire Extinguisher P.A.S.S. –Pull Pin –Aim at base of fire –Squeeze handle –Sweep back and forth

27. Controlling Fire Hazards Flammable liquid safety – Limit quantities –Store liquids in flammable liquid cabinets or rooms –Use "Safety" cans –Ventilation –Pressure relief valves

28. Controlling Fire Hazards Flammable liquid safety –Controlling ignition sources Grounding and bonding Non-sparking tools Approved dispensing hoses Classified "explosion proof" wiring "Hot Work Permit“ –For welding, etc. –Test for LEL –Observer stands by with extinguisher or fire hose

29. Controlling Fire Hazards Fire Suppression Systems –Automatic sprinklers Wet pipe (buildings) Dry pipe (industrial) –Deluge –Dry chemical –CO 2, HALON