HSE Occupational Health and Industrial Hygiene 2 — Questions and Answers
Question 1: Which OSHA permissible exposure limit (PEL) type represents the maximum concentration a worker can be exposed to for any 15-minute period?
- Short-term exposure limit (STEL) (Correct answer)
- Time-weighted average (TWA)
- Ceiling value (C)
- Action level (AL)
Correct answer: Short-term exposure limit (STEL)
A STEL is the maximum airborne concentration permissible during any 15-minute period, not to be exceeded more than four times per shift.
Question 2: A worker is exposed to a noise level of 95 dBA for 4 hours per day. According to OSHA's permissible noise standard, what is the maximum additional hours of exposure at 90 dBA allowed?
- 2 hours (Correct answer)
- 4 hours
- 1 hour
- 0 hours — dose is already exceeded
Correct answer: 2 hours
At 95 dBA the PEL is 4 hours; at 90 dBA it is 8 hours, so the fraction used is 4/4 = 1.0, meaning no additional 90 dBA exposure is allowed without exceeding the dose.
Question 3: What term describes the process of drawing a contaminant-containing air sample through a collection medium at a known flow rate to measure worker exposure?
- Active sampling (Correct answer)
- Passive sampling
- Grab sampling
- Wipe sampling
Correct answer: Active sampling
Active sampling uses a pump to pull air through a sorbent tube, filter, or impinger at a calibrated flow rate over the sampling period.
Question 4: Which biological monitoring marker is most appropriate for assessing recent benzene exposure in a worker?
- Urinary trans,trans-muconic acid (Correct answer)
- Blood lead level
- Urinary mandelic acid
- Exhaled carbon monoxide
Correct answer: Urinary trans,trans-muconic acid
Trans,trans-muconic acid is a specific urinary metabolite of benzene and is the preferred biological exposure index (BEI) for recent benzene exposure.
Question 5: According to the hierarchy of controls, which measure most effectively eliminates an occupational health hazard?
- Substitution of the hazardous substance (Correct answer)
- Engineering controls
- Administrative controls
- Personal protective equipment
Correct answer: Substitution of the hazardous substance
Substitution removes the hazard entirely by replacing it with a less hazardous material, making it the most effective control below elimination.
Question 6: A gas with a vapor density greater than 1.0 tends to accumulate in which location within an enclosed space?
- Low-lying areas and floor level (Correct answer)
- Near the ceiling
- Uniformly throughout the space
- Near air intake vents
Correct answer: Low-lying areas and floor level
Vapors denser than air (vapor density > 1) sink and collect at the lowest points of a space, creating oxygen-deficient or flammable zones near the floor.
Question 7: Which type of ventilation system dilutes contaminated workplace air with fresh air rather than capturing contaminants at their source?
- General dilution ventilation (Correct answer)
- Local exhaust ventilation
- Make-up air system
- Recirculation ventilation
Correct answer: General dilution ventilation
General dilution ventilation introduces fresh air to reduce overall contaminant concentration, unlike local exhaust which captures emissions at the source.
HSE Occupational Health and Industrial Hygiene 2
Which OSHA permissible exposure limit (PEL) type represents the maximum concentration a worker can be exposed to for any 15-minute period?