Most General Duty citations have nothing to do with Ammonia refrigeration but I’ve started to see a trend recently where processes that are not covered by PSM are being subject to Recognized and Generally Accepted Good Engineering Practices (RAGAGEP). The example below is from an organic poultry processor in Georgia:
Even though this company had less than the threshold quantity required for Process Safety Management programs (10,000 pounds for Anhydrous Ammonia) you see they have a General Duty to furnish a place of employment that was free from recognized hazards. Ammonia is a hazard that is generally recognized and an Ammonia detector is a Recognized and Generally Accepted Good Engineering Practice.
You can look up the full citation on OSHA’s website.