CIH Certified Industrial Hygienist (CIH) MCQ 3 — Questions and Answers
Question 1: A confined space is classified as 'permit-required' if it meets which of the following criteria?
- It has limited means of entry or exit only
- It contains or has the potential to contain a serious safety or health hazard (Correct answer)
- It is large enough for an employee to enter and perform work
- It is not designed for continuous occupancy
Correct answer: It contains or has the potential to contain a serious safety or health hazard
A permit-required confined space must meet the basic confined space definition AND contain or potentially contain a serious hazard such as a hazardous atmosphere or engulfment potential.
Question 2: Which sampling strategy should be used to evaluate a worker's worst-case exposure for compliance purposes?
- Random sampling across all workers in a job group
- Worst-case (highest exposure) employee sampling (Correct answer)
- Baseline sampling during average production
- Periodic sampling on random days only
Correct answer: Worst-case (highest exposure) employee sampling
Sampling the worker with the highest expected exposure (worst-case) provides the most conservative data for compliance decisions and overestimates group exposure, protecting all workers.
Question 3: The IDLH concentration for hydrogen sulfide (H2S) established by NIOSH is:
- 10 ppm
- 50 ppm
- 100 ppm (Correct answer)
- 500 ppm
Correct answer: 100 ppm
NIOSH established an IDLH of 100 ppm for H2S, above which escape becomes impaired and life-threatening effects can occur rapidly.
Question 4: Which type of air-purifying respirator is required when the contaminant has poor warning properties (odor threshold above TLV)?
- Half-face respirator with organic vapor cartridge
- Supplied-air respirator
- Powered air-purifying respirator (PAPR)
- Either a supplied-air or self-contained breathing apparatus (SCBA) (Correct answer)
Correct answer: Either a supplied-air or self-contained breathing apparatus (SCBA)
When a chemical has poor warning properties, air-purifying respirators are inappropriate because the wearer cannot detect breakthrough; atmosphere-supplying respirators (SAR or SCBA) must be used.
Question 5: Occupational asthma caused by isocyanates (e.g., TDI, MDI) is best described as which type of immunological reaction?
- Type I IgE-mediated hypersensitivity (Correct answer)
- Type III immune complex-mediated
- Type IV delayed-type hypersensitivity
- Non-immunological irritant response only
Correct answer: Type I IgE-mediated hypersensitivity
Isocyanate-induced occupational asthma primarily involves IgE-mediated (Type I) sensitization, though other mechanisms may contribute.
Question 6: Which formula correctly calculates the ventilation dilution rate (Q) needed to maintain a contaminant concentration below a target level?
- Q = G / C (Correct answer)
- Q = C × G
- Q = G - C
- Q = C / G
Correct answer: Q = G / C
Q (airflow, m³/min) = G (generation rate) / C (target concentration); a safety factor K is typically applied, giving Q = K × G / C.
Question 7: Under the OSHA Hazard Communication Standard (HazCom 2012), Safety Data Sheets must contain how many sections?
- 8
- 12
- 16 (Correct answer)
- 24
Correct answer: 16
GHS-aligned SDSs under HazCom 2012 (29 CFR 1910.1200) must have exactly 16 standardized sections.
CIH Certified Industrial Hygienist (CIH) MCQ 3
A confined space is classified as 'permit-required' if it meets which of the following criteria?