How to Conduct an Occupational Hygiene Assessment: A Practical Framework

Occupational hygiene is the science and art of anticipating, recognising, evaluating and controlling workplace environmental factors that may cause illness, impaired health or significant discomfort in workers. This AREC framework — Anticipation, Recognition, Evaluation, Control — is the foundational methodology applied by every certified occupational hygienist globally, and the structure underpinning regulatory compliance frameworks in Australia.

This guide provides a practical framework for conducting an occupational hygiene assessment, whether you are a certified hygienist, a WHS manager directing a hygiene programme, or a business owner trying to understand what a hygiene assessment involves and what it will produce.

Phase 1: Anticipation

Anticipation involves identifying potential hazards before they are encountered — ideally during the design phase of a workplace, process or task. The goal is to prevent hazards being designed in, rather than engineering them out retroactively. In practice, anticipation involves:

• Reviewing process descriptions, P&IDs, equipment specifications and raw material safety data sheets (SDS) for new projects or process changes
• Consulting relevant regulations, codes of practice, and industry guidance for the process type to identify known hazard categories
• Applying professional knowledge of how similar processes and materials have produced health hazards in comparable operations
• Participating in design reviews, HAZOP studies or MOC (management of change) processes to identify and address hygiene issues at the design stage

Phase 2: Recognition

Recognition involves systematically identifying the actual hazards present in the existing workplace. This is the “discovery” phase of the assessment and involves:

Walkthrough Survey

A systematic physical inspection of the workplace to observe: processes and tasks involving hazardous materials; dust, fume, vapour or noise generating activities; existing controls and their apparent effectiveness; housekeeping conditions; worker behaviours and practices; and areas where formal complaints, health incidents or near-misses have been reported. Notes, photographs and sketches are taken throughout.

Process and Material Review

Review of all safety data sheets (SDS) for chemicals in use, together with process flow diagrams, quantities used, frequencies and durations of exposure-generating tasks. This produces a preliminary chemical inventory organised by route of exposure (inhalation, dermal, ingestion) and exposure potential (routine vs emergency/maintenance tasks).

Worker Interviews

Structured conversations with workers and supervisors about their actual work practices — not just what the procedure says. Workers are often the best source of information about non-routine tasks, process upsets, shortcut practices, and historical incidents that are not captured in documentation.

Record Review

Review of existing exposure measurement records, health surveillance results, incident and near-miss records, maintenance records (particularly for ventilation systems), and regulatory inspection reports. This contextualises the walkthrough findings within the documented history of the workplace.

Phase 3: Evaluation

Evaluation involves determining the magnitude of worker exposure and comparing it to health-based standards (WES values) to assess risk. Two main approaches:

Qualitative Exposure Assessment

Where the hazard level is clearly very low (trace quantities of non-toxic material, tasks of very short duration) or where professional judgment can determine compliance without measurement, a qualitative assessment may be sufficient. This involves estimating exposure potential using a matrix of hazard severity × exposure potential and documenting the reasoning. Qualitative assessments must be defensible and regularly reviewed.

Quantitative Exposure Assessment (Measurement)

For hazards with significant health risk — all WES-regulated airborne contaminants, physical agents such as noise, and complex chemical exposures — quantitative measurement is required. This involves:

• Designing a statistically valid sampling strategy (number of samples, SEGs, sampling duration)
• Selecting appropriate sampling methods (NATA-accredited for WES compliance)
• Collecting samples under representative conditions
• NATA-accredited laboratory analysis
• Statistical analysis of results to estimate the full exposure distribution (not just a single result)
• Comparison of the upper confidence bound of the 95th percentile against the WES

Basic Exposure Assessment Strategy (BEA)

The AIOH and ACGIH both recommend the Basic Exposure Assessment Strategy as a tiered approach: start with a qualitative screening assessment; where hazard potential is not clearly trivial, proceed to preliminary measurements; and where preliminary results do not clearly demonstrate compliance, conduct a full statistical sampling programme with at least 6 samples per SEG.

Phase 4: Control

Control involves selecting, implementing and verifying measures to reduce exposure to ALARP (as low as reasonably practicable). Controls are evaluated and implemented according to the hierarchy:

1. Elimination — remove the hazard entirely
2. Substitution — replace with a less hazardous material or process
3. Isolation — physically separate the hazard from workers
4. Engineering controls — LEV, ventilation, enclosure, noise reduction at source
5. Administrative controls — job rotation, safe work procedures, limiting access
6. Respiratory and personal protective equipment — last resort, supplementary to higher-order controls

Control effectiveness must be verified by re-measurement after implementation. A written corrective action plan with assigned responsibilities, timelines and re-monitoring schedule should document the control implementation process.

Documentation and Reporting

The occupational hygiene assessment must be documented in a formal written report that records: the scope and methodology; all hazards identified and their significance; exposure measurement results and statistical analysis; comparison to WES and other standards; risk rating of each hazard; recommended controls with priority ranking; and monitoring programme recommendations. The report is a legal document and should be dated, authored by a competent person, and retained as part of the workplace health and safety records.