ASP ASP Hazardous Materials and Chemical Safety 2 — Questions and Answers
Question 1: What does the acronym TLV-TWA stand for in occupational exposure guidelines?
- Toxic Level Value - Time-Weighted Average
- Threshold Limit Value - Time-Weighted Average (Correct answer)
- Total Limit Value - Time-Weighted Average
- Threshold Level Value - Total Weighted Amount
Correct answer: Threshold Limit Value - Time-Weighted Average
TLV-TWA (Threshold Limit Value - Time-Weighted Average) is the ACGIH-recommended airborne concentration for a normal 8-hour workday, 40-hour workweek.
Question 2: Using OSHA's 5 dB exchange rate, at what noise level is the maximum permissible exposure time reduced to 1 hour?
- 95 dBA
- 100 dBA
- 105 dBA (Correct answer)
- 110 dBA
Correct answer: 105 dBA
Starting from 90 dBA at 8 hours, each 5 dB increase halves exposure time: 95=4 hr, 100=2 hr, 105=1 hr.
Question 3: What is OSHA's permissible exposure limit for respirable crystalline silica (as quartz) in general industry?
- 50 µg/m³ as an 8-hour TWA (Correct answer)
- 100 µg/m³ as an 8-hour TWA
- 250 µg/m³ as an 8-hour TWA
- 10 µg/m³ as an 8-hour TWA
Correct answer: 50 µg/m³ as an 8-hour TWA
OSHA's 2016 silica rule set the PEL at 50 µg/m³ as an 8-hour TWA for general industry, a significant reduction from the prior limit.
Question 4: A Short-Term Exposure Limit (STEL) is defined as a time-weighted average concentration not to be exceeded over what maximum duration?
- 15 minutes (Correct answer)
- 30 minutes
- 1 hour
- 2 hours
Correct answer: 15 minutes
STEL is a 15-minute TWA concentration that should not be exceeded during any part of the workday.
Question 5: What is OSHA's permissible exposure limit (PEL) for carbon monoxide (CO) in general industry?
- 25 ppm TWA
- 50 ppm TWA (Correct answer)
- 100 ppm TWA
- 200 ppm TWA
Correct answer: 50 ppm TWA
OSHA's PEL for CO in general industry is 50 ppm as an 8-hour TWA per 29 CFR 1910.1000.
Question 6: Which organization publishes Threshold Limit Values (TLVs) as occupational exposure guidelines in the US?
- OSHA
- NIOSH
- ACGIH (Correct answer)
- EPA
Correct answer: ACGIH
The American Conference of Governmental Industrial Hygienists (ACGIH) publishes TLVs annually as recommended exposure guidelines.
ASP ASP Hazardous Materials and Chemical Safety 2
What does the acronym TLV-TWA stand for in occupational exposure guidelines?