Occupational Health, Safety, and Environmental Practices
This domain tests whether you can plan a drywall or plastering task so that workers stay protected and materials are handled responsibly. Expect scenario items: a sanding operation, a removal job in an older building, a scaffold on an uneven floor, or disposal of wash water and scrap.
The control hierarchy drives most answers
Apply controls in order: eliminate (design and knife work that reduce sanding), substitute (wet sanding, low-dust product), engineer (HEPA dust extraction on sanders, negative air, local exhaust), administrative (scheduling, signage, housekeeping), and only then PPE. Options that offer a respirator as the first or only control are usually wrong.
Dust, silica, asbestos, lead
- Respirable crystalline silica comes from sanding cement-based patch and stucco and from cutting masonry. ACGIH's 8-hour TLV is about 0.025 mg/m3, which is very low. Dry sweeping and compressed-air cleaning are unacceptable.
- Joint compound and textured coatings in buildings from before roughly 1990 can contain asbestos, and vermiculite insulation may too. A survey by a qualified person is required before disturbance; if material is suspect, stop work.
- Older paint may contain lead; wet methods, HEPA equipment and hygiene facilities apply.
WHMIS 2015 and respiratory protection
Every product needs a compliant label and an accessible SDS. Respirators require fit testing (CSA Z94.4), user seal checks, and a written program. A disposable mask with no fit test is not a dust-control plan.
Fall protection, ladders, scaffolds
Falls are the leading cause of death in construction. Guardrails with a top rail near 1 m, mid-rail and toe boards; fall protection typically triggers at 3 m (10 ft) in Canadian construction, but confirm the local OHS regulation. Ladders: 4:1 slope, extending about 1 m above the landing, three points of contact.
Worked example
A crew must dry-sand 1,200 sq ft of Level 4 joints in an occupied school, and a subcontractor proposes P100 masks for everyone.
Reasoning: the hazard is gypsum and possibly silica dust, and the mask is the last control. First reduce the need to sand through better knife work and thinner coats. Then engineer it: dust-extracting pole sanders on HEPA vacuums, poly containment with negative air, HEPA final cleaning. Then schedule the work when the building is unoccupied. Fit-tested respirators are added on top, not instead, and air monitoring can confirm the result.
Traps
Treating gypsum dust as harmless; confusing a dust mask with a fit-tested respirator; failing to ask about asbestos in a 1970s building; cleaning with compressed air; storing compound in unlabelled buckets.