Friday, July 07, 2006

Mine Rescue Respirators: Like Being Smothered

Sago survivor Randal McCloy Jr. says four of the air packs his crew was using didn't work after the explosion in the mine.

MSHA says it's tested the air packs manufactured by CSE Corp, and they functioned properly.

And they may both be right, in a weird, tragic way:
Long-term studies of CSE air packs by MSHA and the National Institute for Occupational Safety and Health suggest that while they do create oxygen, they don’t necessarily help miners breathe.
Got that?

OK, let me try to explain it.

For thirteen years its been known that although the CSE packs are light, making them easy for miners to carry, they're very hard to breathe through and they generate high amounts of carbon dioxide, which makes breathing even more difficult. Although the air packs continue to produce oxygen for an hour, almost one-third of those tested stop removing carbon dioxide in half an hour.
The study also found about 20 percent of CSE air packs forced the user to inhale at least 6 percent carbon dioxide — triple the amount allowed by federal regulation.

Carbon dioxide levels should be 4 percent or lower, the study said, because irregular heartbeat and other problems can occur at higher levels. At somewhere around 10 percent, the user likely would pass out.

CSE, however, maintains that its air packs function properly if miners and mine operators follow its inspection guidelines.

Four percent level might be uncomfortable, “but it wouldn’t be intolerable,” said Robert Banzett, an associate professor at the Harvard School of Public Health. “If they can’t breathe more, it’s going to make them feel horribly in need of air.”
CSE and other experts say that miners just need to be trained in what it feels like to breathe through the air packs and instructed to slow their pace when breathing gets difficult.

But some experts don't think that's realistic:
Medical experts say the sensation of suffocating would drive most miners to remove the packs, regardless of the threats they face.

“There is no kind of perception that’s more primal,” said Michael Reid, chairman of the physiology department at the University of Kentucky’s College of Medicine. “It’s a protective response. It’s Darwinian.”
Which may explain why Richard Perry, a Sago miner who escaped alive, said "breathing with a CSE air pack was like being smothered."

So I'm not sure what's more tragic -- that the air packs didn't work, or that because of the way they worked and lack of training, the miners stopped using them when they still contained breathable oxygen.

More mine stories here.