A couple of weeks ago, I had a poll in my FB Group asking:
Is a personal single-gas detector necessary within our breathing zone when wearing an Air Purifying Respirator in a potential IDLH atmosphere? For example, responding to a leak alarm for an NH3 or Cl2 leak.
And as usual, the group did NOT let me down, with 92% of the votes being “Yes”. Even the other 8% made rational comments about why they voted “No”. The question centers around a short phrase used in 1910.119(n).
1910.119(n) Emergency planning and response.
The employer shall establish and implement an emergency action plan for the entire plant in accordance with the provisions of 29 CFR 1910.38. In addition, the emergency action plan shall include procedures for handling small releases. Employers covered under this standard may also be subject to the hazardous waste and emergency response provisions contained in 29 CFR 1910.120 (a), (p) and (q).
You see, NIOSH has been kind enough to QUANTIFY IDLH levels for us, but many fail to DEFINE what those levels mean.
For example, I have a 100′ X 100′ room where the leak is occurring. In that room, I have detectors to notify me of the leak. I have set my detectors at 10% of the IDLH for the chemical. My procedure states that the operator will investigate the leak using a Full-Face APR equipped with a detector for the chemical, worn in their Breathing Zone (BZ). This personal detector, worn in their BZ, is to ensure that we do NOT find ourselves in an IDLH atmosphere.
This means that although I could walk over to the leak point, place the detector right at the leak point, and set it off, since it would be well over the IDLH, the room as a whole is NOT an IDLH atmosphere. The leak is a “small leak” such that, as it diffuses into the atmosphere of my 100′ X 100′ room, it is well below the IDLH.
Here is what OSHA wants…
I have a leak. I have an emergency shutdown SOP for said piece of equipment experiencing the leak. The operator dons their APR w/ the detector worn in their BZ to investigate and ISOLATE the leak. As long as that detector does NOT alarm, they can continue working in the room to address the leak following their Emergency Shutdown SOP for the equipment. But as soon as they try to get to a valve called out in the Emergency Shutdown SOP and their detector goes off, they have to BACK OUT and declare the leak as one which “requires an emergency response.” Now, if the operator arrives at the room and the fixed detectors inside are ALL reading at or above the IDLH, they do NOT even attempt to enter the room; instead, they declare an emergency. But if the entire room is NOT at the IDLH, the operator can enter to investigate using their “everyday PPE” as long as they do NOT exceed the limitations of that PPE. In this scenario, the limitation is the APR, which can not be used in an IDLH atmosphere, which is why we always say that a gas detector worn in the BZ is required in this situation.