Resources / Glossary
Occupational & industrial hygiene glossary
Plain-English definitions of the terms that come up in exposure assessment and hygiene consulting — from SEGs and OELs to Bayesian statistics and respirable silica.
Occupational hygiene
The science of anticipating, recognising, evaluating and controlling workplace health hazards — chemical, physical, biological and ergonomic — that can cause illness or injury. "Occupational hygiene" and "industrial hygiene" describe the same discipline: "occupational hygiene" is the common term in the UK, Australia and New Zealand, and "industrial hygiene" in North America.
Industrial hygiene
The North American term for occupational hygiene — the discipline of anticipating, recognising, evaluating and controlling workplace exposures that can harm worker health.
Exposure assessment
The process of measuring or estimating a worker's exposure to a hazardous agent — such as a chemical, dust or noise — and comparing it against an occupational exposure limit to judge whether the exposure is acceptable.
Similar Exposure Group (SEG)
A group of workers who experience similar exposures because they perform similar tasks in similar conditions. Grouping workers into SEGs lets a hygienist sample representatively instead of monitoring every individual.
Occupational Exposure Limit (OEL)
A regulatory or recommended ceiling on a worker's exposure to a hazardous substance, usually expressed as an airborne concentration averaged over a reference period such as an 8-hour working day.
Time-Weighted Average (TWA)
The average exposure over a defined period — typically an 8-hour working day — weighted by the time spent at each concentration. The 8-hour TWA is the most common basis for comparing an exposure against an OEL.
Short-Term Exposure Limit (STEL)
A limit on exposure averaged over a short period, commonly 15 minutes, used to protect against the effects of brief, high-concentration exposures that an 8-hour average might mask.
Qualitative Risk Assessment (QRA)
A structured judgement of exposure risk based on knowledge of the task, the agent and the controls in place, used to decide whether and where quantitative monitoring is needed.
Chain of custody
A documented, unbroken record of who handled a sample and when — from collection in the field, through transport, to laboratory analysis — so the result can be reliably attributed and defended.
Bayesian exposure statistics
Statistical methods that use Bayesian inference to estimate exposure parameters — such as the probability that exposures exceed an OEL — from limited sampling data, producing credible intervals rather than single point estimates.
Expostats
A set of Bayesian tools for analysing occupational exposure data against exposure limits, developed by researchers including at the Université de Montréal. HazNode builds this methodology directly into its statistics.
Respirable crystalline silica (RCS)
The fine fraction of crystalline silica dust — produced by cutting or grinding concrete, stone and brick — small enough to reach the deep lung, where it can cause silicosis and lung cancer. A priority hazard in construction and mining.
Diesel particulate matter (DPM)
The fine soot and associated chemicals emitted by diesel engines; a recognised carcinogen and a key exposure concern in mining and other diesel-intensive workplaces.
Local exhaust ventilation (LEV)
An engineering control that captures airborne contaminants at or near their source, before they reach a worker's breathing zone. Common in manufacturing and laboratories.
Noise dosimetry
Measurement of a worker's personal noise exposure across a shift using a body-worn dosimeter, used to compare exposure against noise limits and decide on hearing protection.
Exceedance fraction
The estimated proportion of a worker's or SEG's exposures that exceed the OEL — a key output of exposure statistics used to judge whether control is adequate.
See how these come together in practice — read what industrial hygiene software does, or how HazNode handles survey data and Bayesian statistics.
