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Occupational exposure limits and the hierarchy of controls
An occupational exposure limit defines an airborne concentration to which most workers can be exposed over a working lifetime without harm, and reducing exposure starts with eliminating and substituting the hazard – personal protective equipment is the last line, not the first.
Why it matters in the exam
The exam asks definition questions (the 8-hour time-weighted average, the 15-minute short-term limit, the ceiling value), questions on the "action level" – in the Israeli regulations half of the exposure limit, above which monitoring and surveillance are required – and "what is the most effective step to reduce exposure" questions. The right answer to the last type is almost always the highest feasible level of the hierarchy. It also tests that a limit is not a sharp line between safe and dangerous, and that it does not protect every susceptible worker. Limits refer to inhalation only, so skin-absorbed substances are flagged separately, and shifts longer than 8 hours may need an adjusted limit.
Key points
- The exposure limit is an 8-hour time-weighted average.
- The short-term limit refers to 15 minutes; the ceiling must never be crossed.
- In Israel the action level is half the exposure limit and triggers monitoring and surveillance.
- Order of controls: elimination, substitution, engineering, administrative, PPE.
- Personal protective equipment is the last line of defence, because it depends on the fit and correct use by every single worker.
Summary table
| Level in the hierarchy | What is done | Effectiveness | Example |
|---|---|---|---|
| Elimination | The hazard is removed from the process | Highest | Dropping a solvent cleaning step |
| Substitution | A less hazardous substance or process is used | High | Water-based paint instead of solvent-based |
| Engineering control | The worker is isolated from the hazard | High, independent of behaviour | Local exhaust ventilation, wet cutting, enclosed process |
| Administrative control | The way work is done is changed | Moderate | Job rotation, time limits, training, signage |
| Personal protective equipment | Protects the individual worker | Lowest | Fitted respirator, gloves, ear plugs |
A free exam question
מהם מאפייניו העיקריים של המיגון האישי? (the question as examined, in Hebrew)
- א. זהו אמצעי המיגון המועדף לשימוש על העובדים
- ב. מדובר באמצעי מיגון יקר בהשוואה לאחרים אך תחזוקתו קלה יחסית
- ג. מדובר באמצעי מיגון זול יחסית אך מצריך שיתוף פעולה מצד העובד
- ד. אמצעי זה נחשב יעיל יותר בהשוואה לאמצעי מיגון הנדסים
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Sources
- ACGIH, TLVs and BEIs, 2024 — Introduction to the chemical substances TLVs
- NIOSH, Hierarchy of Controls, 2023 — Hierarchy of controls
- Israel Labour Inspection Organization Regulations (environmental and biological monitoring of workers exposed to harmful agents), 2011 — Exposure limits and action level
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.