OSHA TLVs, ACGIH TLVs, or Both
I have never had to work around or in PRCS until now. I should have paid closer attention to it in "Safety 101" (but I knew it did not apply to me at the time - I know "dumb" my bad). So, my knowledge of PRCS is more than a little rusty after 40 + years.
In any case, how much credence do you give the ACGIH TLVs over OSHA TLVs? Which one do you use, or somehow do you use both? For CO the OSHA TLV is 50, ACGIH is 25. I know the OSHA TLVs are over 50 years old and ACGIH are more current.
PS I do not often play in sandboxes I do not have experience, but this one is on the border and a great customer. If if gets more scientific I will call on my CIH contacts.
Comments (5)
Do you mean OSHA PELs? OSHA doesn't have TLVs. Permissible Exposure Limits are published by OSHA and can be enforced by regulations. As you stated, many have not been updated in decades and some are definitely above what we should expose people to.
ACGIH has been updating TLVs over the years as new science comes out about the hazard of different chemicals. OSHA as a section on their website about the use of TLVs. It can be found here.
https://www.osha.gov/annotated-pels/note.
TLVs are not enforceable by OSHA.
Also, California had different PELs than Fed OSHA for some chemicals. Carbon Monoxide being one where the Cal OSHA PEL is 25 ppm.
NIOSH has another set up numbers called recommended exposure limits (REL). These are also not enforceable by OSHA but are more updated than OSHA PEL.
You can't go wrong using TLV from ACGIH as they are usually lower than OSHA PEL.
Agreed, you cannot go wrong with TLVs. For me, it's the value of the peer-reviewed literature that goes into the TLV/BEIs.
Depending on the compound and process involved, well designed control strategies may already get you to the TLV/BEIs.
As others have mentioned, many of OSHA's PELs haven't been updated in 40+ years. However, one place I like to reference is OSHA's chemical database, which lists out OSHA's PELs, NIOSH's RELs, ACGIH's TLVs, as well as Cal/OSHA's PELs. They will also show the STEL and C limits, if applicable. However, I don't know how often this database it updated.
(Here's the link:
https://www.osha.gov/chemicaldatabase
)
Overall, I very rarely rely on OSHA's PELs. It's typically either NIOSH's REL or ACGIH's TLV, whichever one is more stringent without causing unnecessary strain to comply with it.
One thing to keep in mind is that most (not all) PELs are based on long-term exposures, so they may not necessarily make it a PRCS I(due to a "hazardous atmosphere") if the PEL is based solely on chronic health effects. With that being said, NIOSH's REL is based on up to 10-hour days, whereas OSHA and ACGIH are only 8-hour days. If the PEL is based solely on chronic health effects and the confined space has no other serious safety or health hazards, then it would be a non-permit confined space.
As Adele Abrams once told me, if you want to comply, follow OSHA. If you want to protect your workers, follow consensus standards (e.g., NIOSH, ACGIH). The consensus standards are updated regularly based on more recent research, findings, data, etc.
As usual we deal with that though. LOL
TLV would be my recommendation. PRCS are no joke. Where many programs fail is the emergency responce. Make sure that you have a solid plan for responce drills, space reviews and specific training to the hazards involved.