CES Environmental Ergonomics 2 — Questions and Answers
Question 1: The EU Physical Agents (Vibration) Directive sets a daily exposure action value (EAV) for whole-body vibration (WBV) at:
- 0.5 m/s² (Correct answer)
- 1.15 m/s²
- 2.5 m/s²
- 5.0 m/s²
Correct answer: 0.5 m/s²
The EU Vibration Directive sets the daily EAV for WBV at 0.5 m/s² A(8), above which employers must introduce risk reduction measures.
Question 2: In ergonomic lighting design, what is the purpose of using task lighting in addition to ambient (general) lighting?
- To reduce overall energy consumption by eliminating ambient fixtures
- To provide targeted higher illuminance at specific work surfaces without over-lighting the entire space (Correct answer)
- To replace natural daylighting when windows are unavailable
- To eliminate all shadows in the workspace
Correct answer: To provide targeted higher illuminance at specific work surfaces without over-lighting the entire space
Task lighting supplements ambient lighting by delivering higher illuminance exactly where precision work is performed, improving visual comfort without requiring high ambient levels throughout.
Question 3: Relative humidity in an office environment is ideally maintained in which range to balance occupant comfort and minimize health complaints?
- 10–20%
- 30–60% (Correct answer)
- 65–75%
- 80–90%
Correct answer: 30–60%
ASHRAE recommends 30–60% relative humidity to prevent dry mucous membranes at low humidity and mold/respiratory irritation at high humidity.
Question 4: Which control measure is the most effective ergonomic intervention for reducing whole-body vibration exposure in vehicle operators?
- Requiring operators to wear anti-vibration gloves
- Installing a suspension seat with a low-transmissibility rating (Correct answer)
- Scheduling shorter work shifts only
- Applying vibration-dampening floor mats
Correct answer: Installing a suspension seat with a low-transmissibility rating
A suspension seat engineered to isolate the occupant from vehicle vibration is the primary engineering control for WBV, directly reducing the energy transmitted to the spine.
Question 5: An ergonomist discovers that workers near a noisy machine experience noise levels of 95 dBA. Under OSHA's noise standard (29 CFR 1910.95), what is the maximum permissible exposure duration at this level?
- 8 hours
- 4 hours (Correct answer)
- 2 hours
- 1 hour
Correct answer: 4 hours
OSHA's permissible exposure table allows a maximum of 4 hours at 95 dBA before the daily dose reaches 100% and engineering controls or HPDs are required.
Question 6: The 'thermal comfort zone' described in ASHRAE Standard 55 is primarily determined by which combination of factors?
- Air temperature and carbon dioxide concentration
- Operative temperature, humidity, air speed, and clothing/activity levels (Correct answer)
- Surface reflectance and illuminance levels
- Barometric pressure and oxygen concentration
Correct answer: Operative temperature, humidity, air speed, and clothing/activity levels
ASHRAE 55 defines thermal comfort as a function of operative temperature, relative humidity, air speed, metabolic rate, and clothing insulation (clo).
Question 7: Which indoor air pollutant is most commonly associated with 'sick building syndrome' and is primarily emitted from building materials, furniture, and adhesives?
- Carbon monoxide (CO)
- Volatile organic compounds (VOCs) (Correct answer)
- Radon gas
- Particulate matter (PM2.5)
Correct answer: Volatile organic compounds (VOCs)
VOCs off-gassed from paints, carpets, adhesives, and furnishings are a primary contributor to sick building syndrome symptoms such as headaches, eye irritation, and fatigue.
CES Environmental Ergonomics 2
The EU Physical Agents (Vibration) Directive sets a daily exposure action value (EAV) for whole-body vibration (WBV) at: