Part 4 of the Alberta Occupational Health and Safety Act outlines the right to refuse dangerous work and that employees are protected from reprisal for excercising this right. Emplioyees are obligated to refuse dangerous work and inform their employer who is obligated to investigate and implement corrective actions, as required.
Dangerous work is work that involves an ‘imminent danger". Imminent danger can be a danger that is not normal for that type of work or a danger under which a worker in that type of work would not normally do the work. Workers must not perform any job or operate any equipment if they believe there is or will be imminent danger.
The Right to Refuse Dangerous Work Procedure outlines steps that must be followed and documented.
Additional information from Alberta Occupational Health and Safety is available here.