CES Environmental Ergonomics 1 — Questions and Answers
Question 1: According to OSHA's permissible exposure limit (PEL), what is the maximum noise exposure allowed for an 8-hour workday without hearing protection?
- 85 dBA
- 90 dBA (Correct answer)
- 95 dBA
- 100 dBA
Correct answer: 90 dBA
OSHA's PEL for noise is 90 dBA as an 8-hour time-weighted average (TWA); exposure above this requires engineering controls or hearing protection.
Question 2: What is the recommended illuminance level (in foot-candles) for general office tasks such as reading and writing according to the Illuminating Engineering Society (IES)?
- 10–20 fc
- 30–50 fc (Correct answer)
- 70–100 fc
- 150–200 fc
Correct answer: 30–50 fc
IES recommends 30–50 foot-candles (300–500 lux) for general office work such as reading printed materials.
Question 3: Which type of glare occurs when a bright light source is directly within the visual field, causing discomfort or loss of visibility?
- Reflected glare
- Disability glare
- Discomfort glare (Correct answer)
- Veiling glare
Correct answer: Discomfort glare
Discomfort glare causes visual discomfort from a bright source within the field of view, while disability glare actually reduces visual performance.
Question 4: The Wet Bulb Globe Temperature (WBGT) index is used by ergonomists primarily to assess which environmental stressor?
- Noise exposure
- Heat stress (Correct answer)
- Whole-body vibration
- Indoor air quality
Correct answer: Heat stress
WBGT integrates air temperature, humidity, radiant heat, and air movement to provide a composite index for evaluating heat stress risk.
Question 5: According to ASHRAE Standard 55, the recommended operative temperature range for sedentary office work in summer conditions is approximately:
- 64–68°F (18–20°C)
- 70–76°F (21–24°C) (Correct answer)
- 78–84°F (26–29°C)
- 86–90°F (30–32°C)
Correct answer: 70–76°F (21–24°C)
ASHRAE 55 specifies approximately 70–76°F (21–24°C) for sedentary work in summer, accounting for lighter clothing insulation.
Question 6: Which metric is used to describe the strength of a light source's ability to reveal colors accurately compared to a reference light?
- Luminous efficacy
- Color rendering index (CRI) (Correct answer)
- Color temperature (CCT)
- Lux level
Correct answer: Color rendering index (CRI)
The Color Rendering Index (CRI) rates a lamp's ability to reproduce colors faithfully, with 100 indicating perfect rendering compared to a reference source.
Question 7: Hand-arm vibration (HAV) exposure is most closely associated with which occupational health condition?
- Carpal tunnel syndrome
- Raynaud's phenomenon (vibration white finger) (Correct answer)
- Lateral epicondylitis
- Thoracic outlet syndrome
Correct answer: Raynaud's phenomenon (vibration white finger)
Prolonged HAV exposure causes damage to blood vessels and nerves in the fingers, leading to Raynaud's phenomenon (vibration white finger) characterized by episodic blanching.
CES Environmental Ergonomics 1
According to OSHA's permissible exposure limit (PEL), what is the maximum noise exposure allowed for an 8-hour workday without hearing protection?