Hazardous Materials and HAZWOPER

3.1 Hazardous Materials

Pure chemicals, mixtures, fuels, solvents and paints can all be hazardous materials. They can harm health and safety, so we must know how to protect ourselves from injury, illness and death when we work with or near them.

Flammable and combustible liquids

The property that decides whether a liquid is flammable is its flash point. The flash point is the lowest temperature at which a liquid gives off enough vapour, in a test vessel, to form a flammable mixture with air near its surface.

• A flammable liquid has a flash point below 100 °F (37.8 °C). It can burn at ordinary temperatures, so it needs more care.
• A combustible liquid has a flash point at or above 100 °F (37.8 °C).

Explosive limits

A gas or vapour will burn or explode only within a range of concentration in air.

• The lower explosive limit (LEL), also called the lower flammable limit, is the lowest concentration that will flash or burn when there is an ignition source. Below it, the mixture is too lean to burn.
• The upper explosive limit (UEL) is the highest concentration that will burn. Above it, the mixture is too rich.

Both are given as a percentage of vapour or gas in air by volume.

Labels

Every container or tank of chemicals must carry a label saying what is in it and what the hazards are. A label is any printed, written or graphic material on the container.

1. Never deface or remove a label.
2. Never use an unlabelled container.
3. Placards and tags are also hazard warnings.
4. The manufacturer must provide a safety data sheet.

A label must show the contents, the name and address of the manufacturer, the health and physical hazards, and the protective equipment to use. Under the current standard the label also carries a signal word (Danger or Warning), pictograms and hazard and precautionary statements. See Part 7.

Storage

• No smoking, sparks, welding or open flames where hazardous materials are stored.
• Provide suitable fire control equipment, such as portable extinguishers, where flammable or combustible liquids are stored.
• Keep containers out of direct sunlight, in a cool, well ventilated place.
• Do not store them in stairways, near exits or in any route used to escape.
• Keep containers and portable tanks out of offices, except during building or equipment maintenance, and then only in approved containers or cabinets.
• Ground and bond drums when you transfer flammable liquid from one container to another.
• Remove leaking tanks or containers from the store as soon as practical. Move the contents to a sound container or put the whole container in an approved overpack.

Use and disposal

• No welding, open flames or smoking where flammable liquids are transferred, used, stored or disposed of.
• Keep containers closed when they are not in use.
• Clean up spills at once.
• Ventilate the area so that vapour does not build up.
• Put used rags in a self closing oily waste can.

Working safely

Liquids and gases can escape from tanks and containers at any time, so keep to the highest standard of care. Read the label and the SDS before you handle a chemical, follow the signs and symbols and do not enter areas where you are not authorised to go.

A study aid, not published or endorsed by IOSH or OSHA. Laws and limits differ between countries.