Section 3 - Physical Hazards

What are some examples of a physical hazard?

1. Flammable materials - solids, liquids & gases 2. Combustible liquids 3. Oxidizers 4. Pyrophoric materials 5. Organic peroxides 6. Compressed gases 7. Explosive Materials 8. Unstable materials 9. Water reactives

Define Flammable gases

A gas is flammable if it falls in the following two categories: a. The gas has an LFL of less than 13%, <13% by volume at ambient temperature & pressure. b. The gas whose UFL exceeds its LFL by 12% no matter what the LFL is.

Define a hazardous chemical

A hazardous chemical is any chemical that is a physical or a health hazard.

Define oxidizer

Any chemical capable of initiating or promoting a fire in other compounds through the release of oxygen.

Define combustible liquid

Any liquid with a flash point between 100-200 °F.

Define pyrophoric materials

Any substance - solid/liquid - that can be ignited as a result of contact with oxygen without a source of ignition at temperatures less than 130 °F.

Define water reactives and give an example.

Chemicals that react vigorously with water to produce a toxic or flammable gas. Ex. Sodium Na (s) + H2O ----> NaOH (aq) + H2 (g) -- highly exothermic rxn, can cause H2 (a flammable gas) to ignite.

Define compressed gases

Compressed gases that meet any of the following criteria: Gas pressure > 40 psia at 70 °F Gas pressure > 104 psia at 130 °F regardless of pressure at 70 °F Liquids with a vapor pressure > 40 psia at 100 °F psia - pounds per square inch absolute

Define explosive materials and provide an example

Explosive materials are those that decompose in a sudden, violent chemical reaction with production of heat, pressure and a large quantity of gas. Ex. Nitroglycerine, 1 liter of nitroglyerine = 1000 liters of gas.

Define flammable solids

Flammable solids are chemicals that cause fire through friction, absorption of water, retained heat or a chemical that spontaneous burns vigorously.

What are LFL & UFL?

LFL - Lower flammability limit - Minimum concentration (% vol) of a gas in air that will burn in the presence of a source of ignition. UFL - Upper flammability limit - Maximum concentration (% vol) of a gas in air that will burn in the presence of a source of ignition.

Define organic peroxides

Organic peroxides are any organic compound that contain the peroxyl group -O-O-.

Define unstable materials and provide an example

Unstable materials are chemicals that can undergo vigorous decomposition or polymerization under moderate condition of temperature, pressure or shock. Ex. Ammonium compounds NH4NO3 + heat ----> Nh3 (g) + HNO3 (g)

Define flammable liquids

flammable liquids are chemicals that have a flash point that is less than <100 °F.

Define polymerization and provide an example of a compound that undergoes polymerization.

Polymerization - rapid, uncontrollable production of a chain of polymers. Ex. acrylonitrile

Define Flash Point

The flash point is the minimum temperature at which enough vapor is generated in an open container to support combustion in the presence of a source of ignition.