Hazard Management: Identifying Chemical Hazards

Hazard Definition

• A hazard is anything that can cause death, bodily injury to people, damage to equipment, or delay to operations.

Chemical Hazards

• Chemical hazards are sources that can cause fire, explosion, or toxic/harmful effects on health when exposed.

Fire Hazards

• Causes of fire:
  • Burns
  • Asphyxiation (smoke, toxic fumes)
• Fire triangle: oxidizer, ignition (heat), fuel
• Fire tetrahedron: oxygen, heat, fuel, and chain reaction
• Chemical chain reaction: oxidation of fuel in the presence of O2 with emission of heat and light

Fuel Types

• Liquids: gasoline, acetone
• Solids: wood dust, metal particles
• Gases: hydrogen, propane

Oxidizers

• Liquids: hydrogen peroxide, nitric acid
• Solids: metal peroxides, ammonium nitrite
• Gases: oxygen, chlorine

Ignition Sources

• Sparks
• Flames
• Heat
• Static electricity: contact and separation of 2 surfaces with different conductivity

Preventing Fires

• Equipment bonding and grounding: eliminates charge buildup and potential for electrostatic sparks
• Removing fuel: shut off fuel supply to fires
• Reducing oxygen: foam, displace oxygen with inert gas
• Removing heat: applying water for cooling
• Interrupting chemical chain reaction: capture free radicals using an extinguishing agent

Portable Fire Extinguishers

• 1st line defense to stop fire before it gets out of hands
• Contain a fire until help comes
• Class A: ordinary combustible materials like wood and paper
• Class B: flammable liquids, solvents, oils, paint
• Class C: flammable gases
• Class D: combustible metals
• Class F: cooking media in cooking appliances

Fire Extinguishing Agents

• Water:
  • Removes heat
  • Effective for Class A fires
  • Not for electrical source of ignition
• Foam:
  • Excludes oxygen from burning liquid fires, removes heat
  • Fire can re-ignite if foam breaks down
  • Effective for Class A and B fires
• Inert gases:
  • Displaces oxygen
  • Examples: carbon dioxide, nitrogen
  • Effective for Class A and B fires
• Multipurpose dry chemicals:
  • Excludes oxygen through coating surfaces
  • Monoammonium phosphate
  • Effective for Class A and B fires

Chemical Hazards – Explosions

• Uncontrolled combustion producing rapid increase in temperature and pressure
• Differences between fire and explosion:
  • Combustion occurs at surface (fire) vs. entire fuel (explosion)
  • Slow release of heat energy (fire) vs. rapid release of heat energy (explosion)
  • No pressure wave generated (fire) vs. pressure wave generated due to rapid volume expansion (explosion)

Vapor Cloud Explosions

• Ignition of vapor cloud of flammable material
• Sudden release of large amounts of fuel due to rupture of a pipe or tank
• Formation of large vapor cloud in its flammable range
• Delayed ignition would result in vapor cloud explosion

Boiling-Liquid Expanding-Vapor Explosions

• Pressurized vessel containing a liquid above its boiling point ruptures in a fire and releases pressurized liquid rapidly into the fire
• Fire develops adjacent to a pressurized tank containing a liquid above its boiling point
• Tank ruptures explosively, vaporizing its contents

Dust Explosion

• Rapid combustion of fine solid particles
• Occurs when fine particles are suspended in air and ignited

This quiz covers the definition of hazards, specifically chemical hazards, and their effects on health and safety. It also touches on the fire triangle and tetrahedron, and how chemical chain reactions can lead to hazardous situations.