CIEE Environmental Factors & Human Performance 3 — Questions and Answers
Question 1: A facility switches from fluorescent to LED lighting and workers report more eyestrain. Which LED characteristic most likely causes this if illuminance levels are equivalent?
- Higher flicker rate or low modulation depth at certain dimmer settings (Correct answer)
- Lower color rendering index (CRI < 80)
- Warmer correlated color temperature (2700K vs. 4000K)
- Directional beam angle of LED optics
Correct answer: Higher flicker rate or low modulation depth at certain dimmer settings
LEDs dimmed with incompatible drivers can produce perceptible flicker at frequencies that cause eyestrain and headaches even when average illuminance seems adequate.
Question 2: OSHA's permissible exposure limit (PEL) for noise is 90 dBA as an 8-hour TWA. Using the 5-dB exchange rate, what is the maximum allowable exposure duration at 95 dBA?
- 4 hours (Correct answer)
- 2 hours
- 6 hours
- 1 hour
Correct answer: 4 hours
With the OSHA 5-dB exchange rate, each 5-dB increase halves the allowable exposure time; 90 dBA = 8 h, so 95 dBA = 4 h.
Question 3: Which environmental condition most significantly degrades manual dexterity and increases error rates in precision assembly tasks?
- Hand skin temperature below 15°C (59°F) (Correct answer)
- Relative humidity above 60%
- Ambient noise above 70 dBA
- Illuminance below 500 lux
Correct answer: Hand skin temperature below 15°C (59°F)
Tactile sensitivity and fine motor control decline sharply when hand skin temperature drops below 15°C, directly impairing precision assembly performance.
Question 4: An ergonomist measures CO2 at 1,800 ppm in a conference room where workers report difficulty concentrating. What is the most appropriate corrective action?
- Increase outdoor air supply rate through HVAC to reduce CO2 below 1,000 ppm (Correct answer)
- Install CO2 scrubbers to absorb excess gas without changing airflow
- Reduce occupant density to half and maintain existing ventilation
- Switch from natural to mechanical ventilation only during breaks
Correct answer: Increase outdoor air supply rate through HVAC to reduce CO2 below 1,000 ppm
ASHRAE Standard 62.1 targets CO2 below ~1,000 ppm as a surrogate for adequate outdoor air dilution; increasing fresh air supply is the direct and most effective intervention.
Question 5: Which shift work schedule poses the greatest circadian disruption risk and associated performance decrement?
- Rapidly rotating shifts with counter-clockwise rotation (night → evening → day) (Correct answer)
- Fixed night shift with consistent 11 pm–7 am hours
- Slowly rotating shifts with clockwise rotation (day → evening → night)
- 4 days on / 3 days off fixed day shift
Correct answer: Rapidly rotating shifts with counter-clockwise rotation (night → evening → day)
Counter-clockwise rapid rotation forces the circadian clock to phase-advance, which is physiologically harder than phase-delay, resulting in greater sleep disruption and performance loss.
Question 6: In a cold storage facility at −18°C (0°F), which engineering control most effectively reduces cold stress risk for workers performing manual tasks?
- Radiant heating panels directed at the work zone (Correct answer)
- Insulated floor mats alone
- Mandatory 15-minute warm-up breaks every 2 hours without other controls
- Wind barriers on room perimeters only
Correct answer: Radiant heating panels directed at the work zone
Radiant heating panels provide localized heat at the work surface without warming the entire refrigerated space, directly reducing convective and radiant heat loss from workers.
Question 7: Which noise control strategy follows the hierarchy of controls and addresses the problem at the source?
- Replacing a pneumatic riveter with an electric squeeze riveter (Correct answer)
- Providing workers with foam earplugs rated NRR 29
- Enclosing workers in a sound-attenuating booth
- Installing acoustic baffles in the ceiling above the noise source
Correct answer: Replacing a pneumatic riveter with an electric squeeze riveter
Substituting a quieter process tool eliminates or reduces noise generation at the source, which is the highest level of noise control in the hierarchy.
CIEE Environmental Factors & Human Performance 3
A facility switches from fluorescent to LED lighting and workers report more eyestrain.
Which LED characteristic most likely causes this if illuminance levels are equivalent?