Understanding chemical hazard classes when carrying out a risk assessment

May 14, 2019 Posted by Walter Ingles

Hazard classes are groups of chemicals that have similar properties which create a risk to health and safety. In Australia, a chemical’s hazard class is assigned by the GHS, or the Globally Harmonised System of Classification and Labelling of Chemicals and is displayed on the product label  and Safety Data Sheet (SDS). Identifying and understanding a chemical’s hazard class is one of the first steps in the risk assessment process and is critical to ensuring each hazard is properly managed and controlled. This blog outlines some of the most common hazard classes and the risks they could bring to your job site.

Flammable chemicals

Flammable chemicals are substances which can burn, explode or support a fire and include fuel gases, liquids and aerosols; explosives; oxidisers; and some reactive chemicals. When dealing with flammables you have to identify and understand the following three elements:

  • Fire hazard: first, how the chemical could create a fire. For flammable liquids you’ll need to know the flashpoint (or temperature range in which they can ignite). For flammable gases you’ll need the explosive range (concentration of vapours in the air). For oxidisers and reactive chemicals you’ll need to know the auto-ignition temperature, as well as any incompatible materials and substances.
  • Ignition sources: next, look at the potential ignition sources at your job site. It could be welding and hot work, machinery and plant that generates industrial heat, it could be personal gadgets that conduct static electricity, it could be as simple as a naked flame on a bunsen burner.
  • Fuel: finally, look for anything that could fuel the fire. This could range from refuse and waste, tree branches and nearby vegetation, pallets, or other combustible chemicals.

Flammable chemicals must be managed carefully so that the chemicals are segregated according to the appropriate Australian Safety Standard, and their safety cabinets and bulk stores are located away from combustible materials, refuse and vegetation.

Corrosive chemicals

Corrosive chemicals attack and destroy living tissue so they present a danger to human health, animals and other living organisms. When assessing the health risks presented by corrosive chemicals you need to determine:

  • Entry points: corrosive chemicals can cause devastating burns so first determine if the chemicals could be inhaled (can burn the nose, throat, and lungs), ingested (can burn the mouth, throat, and stomach), or directly contact the skin or eyes (can cause blisters, burns, tissue damage, scarring and blindness).
  • Exposure time: next look at the work processes involving corrosive chemicals and estimate handling and exposure times. The risk will increase as workers handle the chemicals for longer periods of time.
  • Dose and concentration: larger quantities of chemicals at a higher (or pure) concentration will also increase the risk to health and safety.

Corrosive chemicals can damage metals, building materials, wood, and plastics so you’ll need to consider how these chemicals are stored and if they could breach packaging materials or metal cabinets. Some corrosive materials create flammable gases when they attack metals.

Toxic chemicals

Toxic chemicals create a hazard for humans, animals, vegetation, and aquatic life. Their effects can be immediate (poisoning) or delayed (allergies) and can be long term (cancer). The risk to health and safety is a combination of the toxicity, concentration, and the way it could enter the body.

  • Irritants - will aggravate the skin or tissue of living things.
  • Asphyxiants - depletes the oxygen in air.
  • Narcotics - depress the central nervous system and can impair judgement and physical responses.
  • Poisons - can quickly cause death or organ damage.
  • Carcinogens - can induce cancer.
  • Mutagens - can mutate the genes of children of exposed workers or offspring or exposed animals/organisms.
  • Sensitisers - cause allergies and sensitivities with repeated exposure.

When conducting your risk assessment always consider the ways the chemical could enter the body (see corrosive chemicals above) or reach the environment (waste materials, emissions, spillage).

Unstable and reactive chemicals

Unstable chemicals can undergo a spontaneous reaction and present a major risk in chemicals stores, manufacturing and despatch areas. Always check the Safety Data Sheet (SDS) to determine the types of conditions that could trigger a dangerous reaction. These include:

  • Heat - some unstable chemicals will decompose and explode when exposed to heat. Organic peroxides are very sensitive to heat, as is acetylene gas.
  • Pressure - some unstable chemicals can detonate and explode due to changes in pressure. Pressure changes can occur through mechanical shock (like dropping a gas cylinder or striking a container with a hammer). Correct storage is of critical importance.
  • Light - chemicals like chlorine and hydrogen are both sensitive to light and can react explosively.
  • Water - some chemicals can react violently when they absorb or contact water.
  • Incompatible substances - some substances are incompatible with other chemicals (eg, acids and bases) and can create dangerous reactions, heat, fires and explosions.
  • Time - chemicals that have been in storage for long periods of time without use can form peroxides and react violently when opened. Always monitor use-by dates of your chemicals.

Chemical storage and waste disposal are of critical importance when managing unstable and reactive chemicals. You’ll want to ensure the chemicals are properly segregated, and that packaging materials and safety cabinets are constructed from suitable materials.

Environmental hazards

Your risk assessment should consider environmental hazards created through airborne emissions, water-borne waste, accidental chemical spills, or pesticide sprays being absorbed into the soil and vegetation of nearby properties.

Next steps

Are you ready to conduct a full risk assessment on the chemical hazards at your own job site? Why not download our free eBook How to manage the risk of hazardous chemicals in the workplace. We present our full risk management methodology IDENTIFY - ASSESS - CONTROL - SUSTAIN and walk you through all the essential steps to ensuring your chemicals are managed legally and safely. Download and read it today by clicking on the image below:

How to manage the risk of hazardous chemicals in the workplace
Walter Ingles

Walter Ingles Compliance Specialist

Walter is STOREMASTA’s Dangerous Goods Storage Specialist. He helps organisations reduce risk and improve efficiencies in the storage and management of dangerous goods and hazardous chemicals.

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