OSHA updated a 2017 Letter of Interpretation in January 2021 and it is causing quite a stir in the anhydrous ammonia (NH3) fertilizer industry and could have impacts on other industries that use NH3. In this revised LOI, OSHA states…
… Therefore, OSHA believes it is possible, and indeed likely, that any given release of anhydrous ammonia in your scenario will necessitate an emergency response in accordance with the requirements of 29 CFR 1910.120(q). Extremely small vapor releases, such as minor valve packing leakage and similar releases where exposures in the breathing zone of the employee would be less than the PEL and there is no risk of a catastrophic release, may be considered incidental.
I wish to explain the silliness of using the Permissible Exposure Limits to define an “emergency”.
Since 1993 I have always been taught from both a municipal response and an industrial response perspective that we use the IDLH as the turning point to QUANTIFY a release requiring an emergency response. From the first day I landed in a chemical plant, we were faced with drawing the line in the sand between a release that would be “incidental” vs. “one requiring an emergency response” and we used the IDLH for this.
And folks, if you stick your meter (or your face) right at the point of release we can achieve well over the IDLH; but pull the meter back just 1-2′ and the reading drops to even below the PEL. So when we state the room/area is IDLH, this means that we can not be in the area because our “breathing zone” is in an IDLH (e.g. the chemical is in such quantity and concentration that the room/area is an IDLH atmosphere.
In contrast to this, we have a leak that is not of such magnitude that it creates an IDLH atmosphere. We can work to STOP the leak/release wearing our NORMAL PPE and using our NORMAL safe work practices and be FULLY protected while working to stop the release. In other words, we are fully equipped and trained to handle the chemical that is leaking. We very well may be ABOVE the PEL and thus we would don an APR to manage the exposure- EVEN though we would not even exceed the PEL of NH3 (i.e. 50 ppm). PLEASE REMEMBER these PELs are based on an eight-hour time-weighted average (TWA); so we “officially” (albeit silly and stupid) working in more than 50 ppm of NH3 for a brief period of time and NOT exceed the PEL at the end of the day! Using a ceiling limit, like the Immediately Dangerous to Life and Health (IDLH) makes a ton more sense because it is a Ceiling Limit – a limit we can not exceed with NORMAL PPE such as an APR.
As I have written about for years and have been screaming it from the mountain tops to anyone who will listen – the use of an APR really necessitates the use of a PERSONAL MONITOR in your breathing zone. Once the APR is donned, we lose all ability to know when we go from 50 ppm to 300 ppm so the personal meter is a MUST HAVE in order to ensure the workers NEVER exceed the IDLH while using an APR. But you will not find the requirement for a personal monitor in any OSHA standard – but I am not quite sure how else we can ensure this. And PLEASE spare me with the lame debate about using fix detectors in the room/area. I have been in rooms that had process detectors alarming at 500 ppm and our personal detectors never broke 100 ppm. The leak was being pulled by the detector as we placed the detector in the air stream so it would have a faster response to a leak in the room. Fixed detectors are in place to MONITOR the room when the room is unoccupied and then to activate emergency actions if personnel can not respond to the alarm condition in a timely manner.
But for OSHA to claim that a leak that is less than the PEL “may be considered incidental” is quite silly.
See the full LOI HERE