Its 2017 and we still debate the flammability of anhydrous ammonia (NH3). It is a fact that NH3 is not classified as a “flammable gas” due to its high Lower Explosive Limit (16%) and it’s flammable range being less than 12 percentage points. But there is one other fact that we seem to lose sight of… NH3 has an LEL and it will burn! Here is a 2013 OSHA fatality that involved a flash fire with anhydrous ammonia while “draining oil” from the system aboard a fishing vessel…
At 10:45 a.m. on June 24, 2013, an employee was draining oil from a low-pressure receiver that was part of a mechanical refrigeration system. The employee was using a hose to drain the oil from a drain port and anhydrous ammonia was released in a vapor state before igniting. The employee received second and third-degree burns over a significant portion of their body. The initial report does not indicate when the employee died.
The worker, 82, was injured aboard an 86-foot fishing vessel tied up at seafood processor at the time of the incident. He was a 60-year veteran of the fishing industry in Alaska, and co-owned the boat with his son.
The spill-response arm of the Alaska Department of Environmental Conservation said the vessel released upwards of 50 pounds of anhydrous ammonia. The chemical is used in refrigeration systems. No one besides the owner was seriously injured in the accident, although three or four people reported to area hospitals complaining of ammonia-exposure symptoms. Those symptoms include burning of the eyes, nose, and throat.
Sources:
https://www.osha.gov/pls/imis/establishment.inspection_detail?id=915413.015
https://www.kcaw.org/2013/06/24/man-medevacked-after-sitka-ammonia-leak/