Is this confined space safe to enter?
You're monitoring a confined space entry operation where the entrants are using an oxyacetylene torch to cut out a component inside the space that they're going to replace, producing carbon monoxide (CO) as a byproduct of the process. The meter shown in the picture has tubing that is positioned in the same area as the worker. The meter passed a bump test at the beginning of the shift, passed a calibration earlier in the week, and, overall, is functioning properly.
The OSHA PEL for CO is 50 PPM TWA, whereas the NIOSH REL (which is what most CO sensors are programmed to alarm at) is 35 PPM TWA, and the ACGIH TLV is 25 PPM TWA.
Your worker asks if he/she can re-enter the space and continue working. The entire job, from start to finish, is only expected to take approximately six hours. No ventilation equipment is readily available because the crew forgot it at the shop this morning.
Based on the meter's readings, what would you tell your employee? Why or why not?
Let us know in the comments! 👇🏻
Comments (21)
I am not a PRCS expert, but I will take a swing at it. My inclination is to say go for it, and start work but as a by-product is CO to be very careful and monitor their meter. I would tell the attendant to watch it closely and get them out if it gets to 35 ppm or the O2 drops below my personal low of 20. I like a safety factor.
I just know you will correct me, but I gave it a shot.
Related what are the major differences between 1926 Subpart AA and 1910.146?
Is it safe? Or is it a good idea?
Is it safe? Probably not going to kill anyone. The PEL is 50ppm, so legally you could you could be at around 66ppm for 6 hours (alot of 6s there, maybe this isn't such a good idea...)
Is it a good idea? Absolutely not. How long did it take to jump to 24ppm? How long would it take to jump to 50? 100? Even 50 isn't without health effects. The folks exposed could experience respiratory distress, chest pain, and their blood is going to be carrying less oxygen. Assuming it's going to be hot in the space with the welding and gear, that's a recipe for disaster.
IF it were some kind of emergency, you'd have to do a bit of a risk assessment and decide what's worse. With a good non-entry rescue system maybe you decide it's okay to have a young healthy person go for it. Maybe rotate through a few welders if possible.
There are no hard and fast rules here, but this one is a no for me unless there are some pretty serious consequences to delaying the work.
Ironically, I had almost this exact scenario come up as a question today while teaching a confined space entry class.
If it were me, someone would be driving back to the shop to get the ventilation equipment they forgot. Like Tim pointed out, it is likely to continue to increase. Off the top of my head, the STEL for CO is only 200ppm. Its not unreasonable to think that the STEL could be exceeded without proper ventilation.
I'm telling them to get a ventilation fan and get those readings down to as close to 0 ppm as possible. The reading doesn't. give me a warm fuzzy feeling. I would have them go back to the shop and get some ventilation fans regardless. If the job was planned properly, the vents fans would have been on site first thing in the morning.
Is this a leadership failure?
If this was a vertically designed PRCS, too many "competent" persons omit sampling across that stratification, especially prior to their authorized entrants at the lower level begin their ascent up and out of that space on a fixed ladder.
Ventilation can create pockets or the space, by design, has dead spaces where positive pressure fans cannot reach, but the by-products of combustion can.
I am not comfortable with anything reading on the meter that I cannot chase down to a cause. Everybody has given good responses and I won't duplicate. But, let me share a story for added value (I hope). I was asked one night to send somebody up to the 10th floor of a industrial structure to investigate a leaking acetylene cylinder on a welders rolling cart. Sure enough the acetylene cylinder was leaking so my fire guys loaded the entire oxyacetylene cart into the elevator and bring it to ground level.
When they opened the doors on the ground they were both unstable and wabbly and giggling like school girls. The cause? Acetylene is extremely flammable. Whet many don't know is that acetylene is also a narcotic gas. After a few minutes in a clean air atmosphere my colleagues recovered but they had headaches.
https://www.fireengineering.com/leadership/acetylene/#gref
I would definitely instruct the worker not to proceed. When the question is whether it's worth risking lives to get the job done now rather than later, the answer should always be no, no matter how low the risk seems to be at face value. Based on the meter readings and the requirements of the job, it seems highly likely that the work can be completed safely. However, ventilation is an extra layer of protection, a failsafe that's there precisely in case things don't go as expected. It's a six-hour operation, but what if a medical emergency were to occur inside the confined space and someone is unable to exit? This is just a hypothetical, but someone could fall while entering or exiting via the ladder. Even if they're in fall protection, the gear could malfunction and they could be injured. Now you have someone with a potential spinal injury, so you can't move them; you have to wait for emergency services to arrive. They get a flat tire on the way over and are delayed. Now it's no longer 6 hours...
I'm on the safety training and comms side of the business, and this is how we think about safety. You don't put the controls in place for the existing conditions, you put them in place for the worst-case scenario.
Mirroring what others said, I'd be concerned about why CO is elevated. If it's above zero at the face of the confined space, what are we looking at in the space itself. I always carry around some string to tie on and will lower it into the space to look at concentrations across the space. If you can identify source and are able to take a measurement at said source then you may be able to proceed if you're not over at that point. However, you shouldn't have to evac a space if you've done a proper assessment of the exposures. If you're in the hole and the meter starts to alarm, you've missed something in your assessment and follow-up interventions.