If you would not issue a PRCS entry permit to enter a space at 19.6% Oxygen, why the hell are we listing this range (19.5% – 23.5%) as acceptable for an unsuspecting entry supervisor?
Why would we not just use 20% – 21% for an acceptable O2 concentration for an everyday supervisor who usually gets limited training on limitations of the brand/model/style of direct-reading instrument and how atmospheres actually behave. If they get a reading outside this narrow range, I hope we can ALL agree something is going on inside the space and an Atmospheric SME should be called to the space for a more thorough understanding of the HAZ ATM and the limitations of the meter being used.
Now I realize some of you may have all your entry supervisors well trained, but if they can not explain what a 19.5% Oxygen atm is called (e.g. IDLH atm) and explain the Respiratory Protection (SCBA/SAR with escape air) and Staffing requirements for entry and working in an IDLH atm and the Rescue Requirements for this entry (rescue team is stationed at entry portal to affect rescue in less than 3-minutes… how long can you hold your breath) then why would we ever put them in this situation?
I do the same with my LEL%. NEVER use the 10%! Far too many entry supervisors do NOT understand or even know about the limitations of their Direct Reading instrument’s LEL sensor. I have used 2% for nearly 30 years, as the largest correction correlation I have seen was Isobutane @ 4.5. I have seen it too many times in audits and accident investigations: the ES simply takes the LEL meter reading on the screen, and if that number is LESS THAN 10%, they allow entry into the space, even though the REAL level can be as high as 40% of the LEL. By using 2% we have a very good chance that we will NOT be sending workers into a HAZ Flammable ATM (as defined by OSHA).
Another topic to discuss is if the O2 has lost 1% (e.g. its 19.8%), that means there is something else inside the atmosphere and its at 10,000 ppm. The atmosphere inside the space is ALWAYS 100% volume of air, so a loss of 1% oxygen is being replaced with 1% of some other gas. And since 1% = 10,000 ppm, we have to ask, is our 4 or 5 gas direct-reading instrument capable of identifying all the potential gases inside the space? NOPE – it will only tell us the gases the meter is equipped and calibrated to read! Think of all the gases that our meter is NOT capable of reading and that have IDLH limits LESS THAN 10,000 ppm. Damn scary situation and I would bet less than 5% of the Entry Supervisors I have interviewed in my career know any of this.
We can make our PRCS entry programs so much better when we care more about our entrants than we do about meeting OSHA minimums. Changing these limits will have ALMOST ZERO impact in 99% of our entries, but that day when we are outside these new, narrower limits, we may just save a life!
MAKE THE CHANGE TODAY!