If you live in Canada, WorkSafe whom is a lot like OSHA, will be conducting inspections initiative focused on preventing workers from unsafe exposure to ammonia. These inspection are from the recent tragedy and ammonia incident that took 3 lives. There are two great PDFs that WorkSafe has put together in the last few years. We suggest you take a look at both in incorporate some of hazard assessment questions into your own PHA worksheets. WorkSafe has not yet released root cause of the incident, but just released this month a new PDF to employers of recreational facilities that use ammonia as a refrigerant.