CITB Hazardous Substances (COSHH) 2 — Questions and Answers
Question 1: What is the workplace exposure limit (WEL) used for?
- To determine how many workers can be in a confined space
- To set the maximum concentration of an airborne substance workers can be exposed to over a defined period (Correct answer)
- To calculate the maximum weight of chemical containers on site
- To determine the minimum ventilation rate in offices
Correct answer: To set the maximum concentration of an airborne substance workers can be exposed to over a defined period
Workplace Exposure Limits (WELs) are set by HSE in EH40 and define the maximum concentration of an airborne hazardous substance (averaged over 8 hours or 15 minutes for short-term limits) that workers should not exceed.
Question 2: What health risk is associated with prolonged exposure to silica dust on construction sites?
- Leptospirosis
- Silicosis, a serious and incurable lung disease (Correct answer)
- Tetanus
- Legionnaires' disease
Correct answer: Silicosis, a serious and incurable lung disease
Respirable crystalline silica (RCS) dust, generated by cutting, drilling, or grinding concrete, brick, or stone, causes silicosis — irreversible scarring of lung tissue. It also significantly increases the risk of lung cancer. The WEL for RCS is 0.1 mg/m³.
Question 3: How should hazardous substances be stored on a construction site?
- Anywhere convenient as long as they are labelled
- In a secure, ventilated area away from ignition sources with appropriate signage (Correct answer)
- In the site office for easy access
- On the top level of scaffolding to keep them away from ground moisture
Correct answer: In a secure, ventilated area away from ignition sources with appropriate signage
Hazardous substances must be stored in a secure, well-ventilated area away from ignition sources, incompatible materials, and drainage. The storage area should have appropriate signage, spillage containment (bunding), and SDS sheets readily available.
Question 4: What should you do if a hazardous substance is accidentally spilled on your skin?
- Wipe it off with a dry cloth and continue working
- Immediately wash the affected area with plenty of clean water and seek medical advice (Correct answer)
- Apply a plaster over the area
- Wait until your next break to wash it off
Correct answer: Immediately wash the affected area with plenty of clean water and seek medical advice
If a hazardous substance contacts your skin, you should immediately remove contaminated clothing and wash the affected area thoroughly with plenty of clean water. Seek medical advice promptly. Delays can result in chemical burns, dermatitis, or absorption through the skin.
Question 5: What does LEV stand for in the context of controlling hazardous substances?
- Low Energy Ventilation
- Local Exhaust Ventilation (Correct answer)
- Legal Exposure Value
- Limited Equipment Verification
Correct answer: Local Exhaust Ventilation
Local Exhaust Ventilation (LEV) is an engineering control that captures airborne contaminants (dust, fumes, vapours) at or near their source before they spread into the workplace air. Examples include on-tool extraction on cutting equipment and fume extraction hoods.
Question 6: Asbestos is most dangerous when it is in which condition?
- When it is wet and intact
- When it is dry, damaged, or disturbed and fibres become airborne (Correct answer)
- When it is sealed behind paint
- When it is in a locked room
Correct answer: When it is dry, damaged, or disturbed and fibres become airborne
Asbestos is most dangerous when its fibres become airborne, which happens when asbestos-containing materials are damaged, deteriorated, or disturbed (cut, drilled, broken). Inhaled asbestos fibres cause mesothelioma, asbestosis, and lung cancer — all with long latency periods.
CITB Hazardous Substances (COSHH) 2
What is the workplace exposure limit (WEL) used for?