ACI Environmental & Worker Safety 2 — Questions and Answers
Question 1: What is the OSHA permissible exposure limit (PEL) for respirable crystalline silica over an 8-hour shift?
- 0.05 mg/m³ (Correct answer)
- 0.5 mg/m³
- 1.0 mg/m³
- 5.0 mg/m³
Correct answer: 0.05 mg/m³
OSHA's PEL for respirable crystalline silica is 0.05 mg/m³ as an 8-hour time-weighted average.
Question 2: When working with concrete in hot weather, which condition most increases the risk of heat stroke for finishers?
- High humidity combined with high temperature (Correct answer)
- Low wind speed only
- Direct sunlight only
- High altitude work
Correct answer: High humidity combined with high temperature
High humidity prevents sweat from evaporating effectively, reducing the body's ability to cool itself and dramatically increasing heat stroke risk.
Question 3: Which type of respirator provides the highest level of protection against concrete dust containing silica?
- N95 filtering facepiece (Correct answer)
- Surgical mask
- Paper dust mask
- Single-strap nuisance mask
Correct answer: N95 filtering facepiece
An N95 respirator filters at least 95% of airborne particles and is the minimum NIOSH-approved option recommended for silica dust exposure.
Question 4: Concrete washout water is classified as what type of waste requiring proper disposal?
- Alkaline hazardous waste (Correct answer)
- Non-hazardous solid waste
- Inert mineral waste
- Biodegradable organic waste
Correct answer: Alkaline hazardous waste
Concrete washout water has a very high pH (11–13) and is classified as an alkaline hazardous waste that must not be discharged to storm drains.
Question 5: What does the SDS (Safety Data Sheet) Section 8 specifically address?
- Exposure controls and personal protective equipment (Correct answer)
- First aid measures
- Physical and chemical properties
- Regulatory information
Correct answer: Exposure controls and personal protective equipment
SDS Section 8 covers exposure controls including OELs, engineering controls, and required PPE for safe handling.
Question 6: A concrete finisher notices a co-worker showing signs of alkali burns from wet concrete. What is the immediate first aid action?
- Flush affected area with large amounts of clean water for at least 20 minutes (Correct answer)
- Apply a neutralizing acid solution to the burned area
- Cover the burn with dry dressing and wait for EMS
- Rub the area with a dry cloth to remove concrete residue
Correct answer: Flush affected area with large amounts of clean water for at least 20 minutes
Prolonged flushing with clean water dilutes and removes the alkaline material, which is the correct first aid response before medical attention.
Question 7: Under OSHA's Silica Standard for construction (29 CFR 1926.1153), which control method is listed as the preferred hierarchy over all others?
- Engineering controls such as water suppression or local exhaust ventilation (Correct answer)
- Administrative controls like job rotation
- Respiratory protection
- Warning signs and barriers
Correct answer: Engineering controls such as water suppression or local exhaust ventilation
OSHA's hierarchy of controls places engineering controls at the top, meaning wet methods or LEV must be implemented before relying on respirators.
ACI Environmental & Worker Safety 2
What is the OSHA permissible exposure limit (PEL) for respirable crystalline silica over an 8-hour shift?