Hazardous Area Classification (Fire and Explosion Prevention)
From the perspective of WorkCover Queensland, the purpose of conducting a Hazardous Area Classification (HAC) is to minimize the risk of an explosive or flammable atmosphere coming into contact with an ignition source. This objective is achieved by:
- Assessing the risk of fire and explosion hazards in and around installations and plants dealing with flammable liquids, vapors, gases, and combustible dusts.
- Establishing zones where explosive atmospheres are anticipated, determining their size, and identifying ignition characteristics.
- Categorizing the minimum level of ignition source protection required for equipment in a hazardous area to control the risk of fire or explosion.
A hazardous area is defined as a three-dimensional space where a flammable or explosive atmosphere may be present, requiring controls for ignition sources to manage safety risks, such as fires and explosions. The consequences of fire and explosion can be severe, causing harm to people, property, and potential business loss.
The duty of care, as outlined in electrical safety and work health and safety legislation, is imposed on a person conducting a business or undertaking (PCBU) due to the critical nature of managing hazardous areas.
Hazardous area classifications can be performed by direct comparison with typical installations or through more quantitative methods that may involve detailed plant knowledge. New or complex installations may necessitate additional hazard identification processes, such as Preliminary Hazard Analysis (PHA) and Hazard and Operability Study (HAZOP), along with calculations using specialized modeling software.
Representative data on the explosive properties of flammable materials, including manufacturer's safety data sheets (SDS), must support HACs. Additionally, classifications involving combustible dusts may require testing to determine properties such as particle size and chemical composition.
To control risks, the initial step is conducting a hazardous area classification to identify locations where flammable atmospheres may exist and implementing measures to eliminate or control potential ignition sources. Sources of release of flammable substances can occur through constant activities, occasional operations, or unplanned events. It's crucial that hazardous area classifications are carried out by qualified individuals.
The Managing Risks of Hazardous Chemicals in the Workplace Code of Practice 2021 refers to specific Australian Standards for classifying hazardous areas:
- AS/NZS 60079.10.1 Explosive Atmospheres - Classification of Areas - Explosive Gas Atmospheres
- AS/NZS 60079.10.2 Explosive Atmospheres - Classification of Areas - Explosive Dust Atmospheres
Hazardous area classifications are dynamic documents that should be consulted during new installations, site inductions, change assessments, inspection, maintenance, repair activities, and periodic reviews.