OHST Industrial Hygiene & Exposure Assessment 2 — Questions and Answers
Question 1: What type of air sampling is used to measure contaminant concentrations specifically in a worker's breathing zone?
- Area sampling
- Personal sampling (Correct answer)
- Grab sampling
- Perimeter sampling
Correct answer: Personal sampling
Personal sampling places the sampling device in the worker's breathing zone so it travels with the worker, accurately capturing actual individual exposure.
Question 2: A 'grab sample' in air monitoring is best described as:
- A sample collected over an entire 8-hour work shift
- A sample collected at a fixed location with no worker present
- A sample collected over a short, defined time period (Correct answer)
- A sample taken at the boundary of the work area
Correct answer: A sample collected over a short, defined time period
A grab sample captures air quality at a specific point in time over a brief collection period, providing a snapshot of instantaneous conditions.
Question 3: Which sampling media is most commonly used to collect organic vapors for subsequent laboratory analysis?
- HEPA filter
- Activated charcoal tube (Correct answer)
- Polyvinyl chloride (PVC) filter
- Mixed cellulose ester filter
Correct answer: Activated charcoal tube
Activated charcoal tubes adsorb organic vapors efficiently; the sample is then desorbed with solvent and analyzed by methods such as GC-MS.
Question 4: Which instrument provides real-time, direct readings of airborne particulate concentrations without laboratory analysis?
- Midget impinger
- Direct-reading photometer or optical particle counter (Correct answer)
- Activated charcoal tube
- Bubblers and impingers
Correct answer: Direct-reading photometer or optical particle counter
Direct-reading instruments such as photometers and optical particle counters measure light scatter or attenuation to instantly report airborne particulate concentrations.
Question 5: OSHA's action level for occupational noise exposure, which triggers hearing conservation program requirements, is:
- 80 dBA as an 8-hour TWA
- 85 dBA as an 8-hour TWA (Correct answer)
- 90 dBA as an 8-hour TWA
- 95 dBA as an 8-hour TWA
Correct answer: 85 dBA as an 8-hour TWA
OSHA's noise action level is 85 dBA as an 8-hour TWA; at or above this level, employers must implement a hearing conservation program.
Question 6: In biological monitoring, what is being measured to evaluate worker exposure?
- Airborne concentration of hazardous substances near the worker
- Surface contamination levels in the surrounding work area
- Chemical substances or their metabolites in body fluids or tissues (Correct answer)
- Real-time noise levels recorded near the worker's ears
Correct answer: Chemical substances or their metabolites in body fluids or tissues
Biological monitoring assesses the internal dose by measuring chemicals or their metabolites in blood, urine, or exhaled air, reflecting actual absorption.
Question 7: A colorimetric detector tube works by:
- Capturing particles on a filter for gravimetric weight analysis
- Producing a visible color change in a reagent as the target gas passes through (Correct answer)
- Ionizing gas molecules for detection by an electronic sensor
- Measuring the infrared absorption spectrum of the collected sample
Correct answer: Producing a visible color change in a reagent as the target gas passes through
Colorimetric detector tubes contain reagents that react with the target substance to produce a color change proportional to the concentration present.
OHST Industrial Hygiene & Exposure Assessment 2
What type of air sampling is used to measure contaminant concentrations specifically in a worker's breathing zone?