Occupational Health, Safety and Environmental Practices
This domain tests whether you can take a gas job from hazard assessment to safe completion: recognizing hazards, applying provincial OHS legislation and WHMIS 2015, controlling energy, entering confined spaces, responding to gas leaks and carbon monoxide events, and limiting releases to air, soil and water.
Core rules and concepts
- Worker rights and employer duties. Know, participate and refuse unsafe work; the employer must supply hazard assessments, training, SDS access, incident investigation and supervision. A certified Gasfitter is treated as a competent worker expected to identify and control hazards independently.
- WHMIS 2015. Sixteen-section SDS and GHS pictograms. Natural gas and propane are Category 1 flammable gases and simple asphyxiants; propane SDS also warns of frostbite from liquid contact.
- Physical behaviour drives the emergency plan. Natural gas (SG about 0.6) rises and collects at ceilings; LEL near 4–5%, UEL near 15%. Propane (SG about 1.5) sinks into basements, pits, sumps and valve boxes; LEL near 2.1%, UEL near 9.5%.
- Confined space. Test before entry (oxygen 19.5–23%), monitor continuously, use an attendant, permit and rescue plan. Never enter to rescue without respiratory protection.
- Lockout. Isolate gas, electricity and air, verify zero energy, tag and try. A closed valve is not a lock.
- Leak response. Clear ignition sources, do not operate switches or use phones inside the space, evacuate, notify the utility and emergency services, and isolate at the meter or tank only if it is safe. Locate leaks with a calibrated combustible-gas meter or soap solution, never a flame.
- Environment. Methane is a potent greenhouse gas: avoid unnecessary blowdown, purge to a safe outdoor location, contain oil and glycol spills, and dispose of mercury thermostats, asbestos gaskets and old refractories under the applicable regulation.
Worked example
A technician is called to a basement boiler room for a gas odour; the boiler is propane-fired. Correct approach: stop at the doorway and read the atmosphere with the meter before entering. If the reading exceeds roughly 10% LEL, do not enter - clear the building, eliminate ignition sources at the panel, isolate propane at the remote tank shutoff and call the supplier. If entry is safe, ventilate with intrinsically safe equipment, leak-test with soap and repair before relighting. Reasoning: propane pools at floor level, so a head-height sniff proves nothing, and a light switch or phone can ignite the pocket.
Traps that cost marks
Stating that natural gas is heavier than air; entering a pit without a test; treating odour as proof that concentration is harmless (odour fade); calling a CO alarm a nuisance instead of investigating combustion air, venting or spillage; and venting a purge indoors.