Occupational Skills and Safety
This domain tests the regulatory framework, hazard recognition, and safe work procedures a trailer technician applies every shift. Expect questions on energy isolation, PPE selection, air-system safety, and the standards that govern commercial trailer work in Canada.
Regulatory foundation
- Federal and provincial OHS law (Canada Labour Code Part II where federally regulated) requires a hazard assessment before work and the right to refuse unsafe work.
- WHMIS 2015 governs labelling and safety data sheets for shop chemicals; TDG applies when trailers carry dangerous goods; the National Safety Code covers commercial vehicle maintenance and inspection.
- CMVSS and CSA standards define trailer equipment requirements, not shop preference.
Stored energy is the core hazard
A parked trailer stores energy in four forms: compressed air (system pressure up to about 120-135 psi), springs (spring brake chambers and suspension), gravity (raised decks, dump boxes, hydraulic cylinders), and electricity.
- Chock wheels, disconnect the tractor, and drain air reservoirs before working on the air system.
- Cage or otherwise neutralize spring brakes before removing a chamber; the spring remains compressed even with air drained.
- Support any raised trailer or component on rated stands or cribbing. Landing gear is a parking support, never a jack stand.
- Relieve hydraulic pressure before opening lines; support cylinders mechanically.
PPE and shop hazards
Safety glasses with side shields, face shield for grinding or air tools, hearing protection, safety boots, and gloves matched to the task. Brake dust may contain contaminants: use a wet method or vacuum, never compressed air. Jacks must be rated, on a level hard surface, and paired with stands.
Worked example
A technician must replace a brake chamber on a loaded van trailer inside the shop. Reasoning: chock the wheels and confirm the trailer is stable; drain the reservoirs and confirm zero pressure at the chamber; cage the spring brake; mark and cap the lines; then remove the chamber. The load stays on the trailer, so no jacking is needed - the trailer rests on its suspension and landing gear, which is acceptable only because no one goes underneath.
Traps that cost marks
The most common errors are treating landing gear as a support, assuming a disconnected glad hand means no stored pressure, skipping the cage step, and using compressed air to clean brake assemblies. Also watch for questions that confuse the right to refuse with the duty to report.