Almost every safety professional on the planet that works with chemicals, emergency response, and confined spaces knows that the Immediately Dangerous to Life and Health (IDLH) exposure is a game changer! But so many also struggle with what it means to actually work in an IDLH atmosphere. In this article, I want to try and explain what it means to respond to an UNCONTROLLED release of a hazardous material/chemical in order to ascertain if the release is
- INCIDENTAL, or
- one that requires an EMERGENCY RESPONSE
OSHA defines incidental as:
a release of a hazardous substance which does not pose a significant safety or health hazard to employees in the immediate vicinity or to the employees cleaning it up, nor does it have the potential to become an emergency within a short time frame
Did you know that OSHA breaks down “uncontrolled releases” into three (3) categories? And it is HOW we decide our uncontrolled release fits which category is what I am going to explain.
- those that are “purely incidental”
- those that “may be incidental or require emergency response depending on the circumstances” and
- “releases requiring an emergency response
In order to establish which category our release falls into, we MUST ALWAYS ASSUME the uncontrolled release is hazardous UNTIL such time we have RELIABLE DATA that says otherwise!
Here is the scenario and how this scenario gets measured and managed when it falls into these three(3) categories:
There is a leak of an HHC/EHS in a room with workers. This HHC/EHS has excellent warning properties and this allows the workers to recognize there is a leak and they exit the room and report the release. You are called to “find the leak” in the room.
We respond to the report of the leak with AT LEAST an Air Purifying Respirator and a CALIBRATED DIRECT reading instrument. We can use the APR with the proper cartridges, training, and fit-test as long as we stay within the LIMITATIONS of our PPE, mainly the APR. The main driving force in this scenario will be the HHC/EHS that has been released has a relatively LOW IDLH and we all know that we can NOT use an APR in an IDLH atm. For the sake of discussion, let’s say our HHC/EHS has an IDLH of 100 ppm.
So this room we are about to enter with our APR and Direct reading instrument for this HHC/EHS is around 65,000 sq feet and the leak is at the ceiling area which is 30 feet high.
Scenario 1A:
As we enter the room, our meter immediately picks up the HHC/EHS, but at a very low concentration of 5-7ppm (i.e. around the odor threshold of the HHC/EHS). As we being to explore the room looking for the leak (remember we know which chemical is leaking as the workers were alerted to it by the distinct odor) our meter is bouncing around 5-15 ppm, well within the limitations of our APR and at a level where skin contact is not a concern.
We find the leak at a flange and the worker takes the direct reading instrument and places the instruments probe an inch from the flange and the meter goes into alarm and reads 750 ppm. As soon as the worker pulls the meter probe back to 36″ the meter falls to 50 ppm. He places the probe into his breathing zone and the meter reads 25 ppm. Remember he is standing in a room that 65,000 sq ft, of which an area of fewer than 25 sq ft does he get readings at levels that would require respiratory protection and is NOT an IDLH atmosphere.
The worker is able to stop the correct the leaking flange with a simple examination/testing with a torque wrench. It is all over with in 10 minutes, the room is ventilated to get it to ZERO ppm, and production resumes within 30 minutes.
Scenario 1B:
As we enter the room, our meter immediately picks up the HHC/EHS a level EXCEEDING the PEL of 25 ppm. As we being to explore the room looking for the leak (remember we know which chemical is leaking as the workers were alerted to it by the distinct odor) our meter is bouncing around 25-75 ppm, well within the limitations of our APR and at a level where skin contact is not a concern.
We find the leak at a flange and the worker takes the direct reading instrument and places the instruments probe an inch from the flange and the meter goes into alarm and reads 750 ppm. As soon as the worker pulls the meter probe back to 36″ the meter falls to 150 ppm. He places the probe into his breathing zone and the meter reads 100 ppm. Remember he is standing in a room that 65,000 sq ft, of which an area of fewer than 25 sq ft does he get readings at levels that EXCEED his APR.
He MUST evacuate the IDLH zone but does he have to evacuate the 65,000 sq ft room, which outside of that 25 sq ft zone, the levels of the chemical are well below the IDLH level of 100 ppm.
Does the worker have to evacuate the 65,000 sq ft room?
Or may he take defensive actions within the room, but OUTSIDE of an IDLH atmosphere, such as closing two (2) valves to isolate the leaking flange?
One thing is PERFECTLY CLEAR, he can NOT attempt to stop the leak at its point-source as that would place him in an IDLH atmosphere for which is NOT properly equipped to work in. But he can back away from that IDLH ZONE and as long as he is following Emergency Shutdown Procedures AND he has made management aware of the situation, safely closing the two isolation valves may very well stop a small incident from becoming a major incident.
He is successful in closing the two (2) isolation valves and the team just waits for the piping to vent all of the HHC/EHS into the space. Even then, the quantity released into such a large space does not make the space an IDLH atmosphere! But the team ventilates the space, applies lockout devices to the two isolation valves and then proceeds to correct the leaking flanges as a MAINTENANCE task – NOT an emergency response.
Scenario 1C:
As we enter the room, our meter immediately picks up the HHC/EHS a level EXCEEDING the IDLH of 100 ppm. IMMEDIATELY TURN AROUND AND EXIT the room and sound the alarm, declaring this release as one requiring an emergency response.
Because that worker had to exit the room because they were not EQUIPPED or STAFFED to work in an IDLH atmosphere and they had to call for help – this makes it clear that it is a release requiring an EMERGENCY RESPONSE.
Notice that all my scenarios involved a pipe and leaking flange. What if the leak was from a 10,000-gallon pressure vessel? Does this change our assessment? ABSOLUTELY, as it changes the quantities available to be released within the room and the lack of ability to safely ISOLATE that quantity from leaking. This is why those workers who are sent to investigate odors/leaks of HHC/EHS MUST be properly trained in how to size up an uncontrolled release. The same level of a leak from different containers may very well be the breakpoint from one being an incidental release (due to the small quantities involved) vs. the same size leak being an emergency (due to the large quantities involved).