There is a “Note” in OSHA’s Permit-Required Confined Space (PRCS) Standard(s) that seems to be overlooked by many who read the standard. This “Note” is maybe the most important “Note” I have come across over my nearly 30 years in safety, so I am at a loss as to why so many misunderstand or overlook the “Note”. The “Note” states:
NOTE: An atmospheric concentration of any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects is not covered by this provision.
I hold this “Note” dear as it is in reference to atmospheric hazards associated with PRCS’s. To be 100% open and fair, this is where and how the “Note” appears in 1910.146(b)
“Hazardous atmosphere” means an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space), injury, or acute illness from one or more of the following causes:
(1) Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL);
(2) Airborne combustible dust at a concentration that meets or exceeds its LFL;
NOTE: This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet (1.52 m) or less.
(3) Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;
(4) Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Subpart G, Occupational Health and Environmental Control, or in Subpart Z, Toxic and Hazardous Substances, of this Part and which could result in employee exposure in excess of its dose or permissible exposure limit;
NOTE: An atmospheric concentration of any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects is not covered by this provision.
This is how it is presented in the Construction PRCS standard:
Hazardous atmosphere means an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space), injury, or acute illness from one or more of the following causes:
Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL);
Airborne combustible dust at a concentration that meets or exceeds its LFL;
Note to paragraph (2) of the definition of “Hazardous atmosphere”. This concentration may be approximated as a condition in which the combustible dust obscures vision at a distance of 5 feet (1.52 meters) or less.
Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;
Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in subpart D of this part (Occupational Health and Environmental Control), or in subpart Z of this part (Toxic and Hazardous Substances), and which could result in employee exposure in excess of its dose or permissible exposure limit;
Note to paragraph (4) of the definition of “Hazardous atmosphere”. An atmospheric concentration of any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects is not covered by this definition.
Any other atmospheric condition that is immediately dangerous to life or health.
Note to paragraph (5) of the definition of “Hazardous atmosphere”. For air contaminants for which OSHA has not determined a dose or permissible exposure limit, other sources of information, such as Safety Data Sheets that comply with the Hazard Communication Standard, § 1926.59, published information, and internal documents can provide guidance in establishing acceptable atmospheric conditions.
So we can see that these “Notes” are key to the definition of a Hazardous Atmosphere, as defined in the PRCS standards. We have to keep in mind that a HAZ ATM inside a CS is especially dangerous and MUST BE evaluated by a competent person. A HAZ ATM inside a CS/PRCS is viewed different and with a higher degree of concern. This is NOT to make light of the same HAZ ATM when it is posing a hazardous OUTSIDE of a CS/PRCS. For example, one that OSHA uses in their discussions of the topic, Asbestos is a SERIOUS hazard and one that has earned our respect and concern. However, overexposure to Asbestos, as bad as it is, is NOT an exposure/HAZ ATM that would make a CS a PRCS.
Yes, the definition of a HAZ ATM makes reference to:
Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Subpart G, Occupational Health and Environmental Control, or in Subpart Z, Toxic and Hazardous Substances, of this Part and which could result in employee exposure in excess of its dose or permissible exposure limit;
And this is where the “Note” plays a CRITICAL role in the definition. The “Note” makes it clear that OSHA is talking of a HAZ ATM that has an ACUTE RESPONSE and will limit the entrant(s) ability to self-rescue. Asbestos, as a bad as it is, has a “chronic response” and would not cause death, incapacitation, impairment of ability to self-rescue, injury, or acute illness due to its health effects EVEN when the entrants may be overexposed.
Now there are some that want to manage an overexposure to a chronic response chemical as a PRCS entry and that is perfectly their decision to go above and beyond the OSHA minimums. I do it all the time and have written extensively about how I go well above OSHA minimums on LOTO and PRCS matters. But these decisions are NOT an OSHA requirement and when we cry wolf that it is an OSHA requirement and we are shown to be wrong, it hurts our credibility as a profession.
So what kind of chemicals would cause a HAZ ATM at its PEL, but below it’s IDLH, in which the entrant could die, become incapacitation, or be impaired of their ability to self-rescue?
I’ll follow this up later over the holidays.
