Comments on: miner safety

Question: miner safety

The Jesse Helms — Thu, 05 Jan 2006 10:02:05 -0800

Why don't miners carry an oxygen tank?

By: The Jesse Helms

The Jesse Helms — Thu, 05 Jan 2006 10:03:56 -0800

This article indicates officials said each of the trapped miners was equipped with a mask and small oxygen tank holding one hour of oxygen. Maybe the danger cannot be mitigated, like a saw to a lumberjack's hand?

By: MrMulan

MrMulan — Thu, 05 Jan 2006 10:03:57 -0800

Just a guess...they could ignite in an enclosed space.

By: The Jesse Helms

The Jesse Helms — Thu, 05 Jan 2006 10:05:43 -0800

A 5 pound tank is good for almost 5 hours. Has Upton Sinclair really been dead so long?

By: wackybrit

wackybrit — Thu, 05 Jan 2006 10:13:18 -0800

Or better, why not have an oxygen generator on hand (like on a plane)?

By: bonehead

bonehead — Thu, 05 Jan 2006 10:14:55 -0800

Compressed air takes up too much space. A single tank, the size fire-fighters use, lasts between 30 and 45 minutes. It's possible to wear two, but one + mask and regulator is very tiring to work in.

Instead, miners carry an "oxygen candle" which is is much smaller and produces usable oxygen much longer, 2 to 5 hours typically. They weigh up to about ten pounds or so and are the size of a large thermos. These use perchlorates, which when wetted by the water in breath, release oxygen and a lot of heat. They're also single use, somewhat dangerous and rather expensive, which is why you don't see them in other uses.

Slate has a decent article on them right now.

By: bonehead

bonehead — Thu, 05 Jan 2006 10:19:17 -0800

That article is wrong to call it a tank, TJH. There's no way that a "small oxygen tank" could "hold... one hour of oxygen..." for an average male even just walking around, let alone doing the heavy work you'd expect just after a cave-in. No, they were using SCSRs.

By: teece

teece — Thu, 05 Jan 2006 10:39:02 -0800

As my dad used to always drum into my head: oxygen is not flammable. It is necessary for combustion, but the oxygen itself will not "burn" in the sense that is usually meant with that word. It's the (very necessary) oxidizer in the burning of something else, but it was going to already have been present in the mine anyway, so it doesn't seem like a huge deal to carry a tank around. Or maybe it is, I dunno. Maybe an academic point here, but my dad would be mad if I didn't say it.

But the reason seems simple to me: an oxygen tank is pretty darn heavy, and would not last a single shift. It's the same reason some guys learned to climb Everest without oxygen -- because without the huge weight of the tanks, they could do it in days, rather than months, even though they could barely function at 29k feet with no supplemental oxygen.

By: Kirth Gerson

Kirth Gerson — Thu, 05 Jan 2006 10:42:44 -0800

bonehead, are these "candles" a kind of rebreather, then?

By: bonehead

bonehead — Thu, 05 Jan 2006 10:46:41 -0800

teecee, the reason I put "candle" in scare quotes is that it really isn't a combustion reaction in the normal sense. It's composed of a superoxide that releases pure O₂ when hydrated. It's very exothermic, to the point that skin burns are a problem with these devices. The Wikipaedia has a short article on it, but doesn't really describe the chemistry. Hmmm. If you're really curious I could dig up some references, but that would take a while.

By: bonehead

bonehead — Thu, 05 Jan 2006 10:49:46 -0800

No, Kirth, they're chemical generators. They don't scrub carbon dioxide.

By: teece

teece — Thu, 05 Jan 2006 10:52:59 -0800

bonehead, I was actually thinking about what MrMulan said, rather than your candle comment. These oxygen candles sound cool, even if they're not actually burning in the way an actual candle does.

By: mmdei

mmdei — Thu, 05 Jan 2006 11:13:51 -0800

What about numerous 'spares' throughout the mine?

By: justkevin

justkevin — Thu, 05 Jan 2006 11:21:10 -0800

I went on a tour of an active mine in Australia several years back. As I recall, all miners had portable breathing units (probably an SCSR) which they could rely on in an emergency. I think we carried them as well.

In the case of the Virginia tragedy, lack of oxygen wasn't the biggest problem, it was the presence of carbon monoxide. At levels of 1300 ppm, even with plenty of oxygen, the miners would lose consciousness within a few hours and die shortly thereafter.

By: designbot

designbot — Thu, 05 Jan 2006 12:36:24 -0800

Everybody's giving very smart answers, but the question doesn't make any sense. The Jesse Helms asks:

Why don't miners carry an oxygen tank?

and then links to an article that says miners carry oxygen tanks. Am I missing something?

By: dhartung

dhartung — Fri, 06 Jan 2006 00:56:45 -0800

Note that perchlorate candles are the preferred oxygen generator by the Russian space program, and were responsible for the fire aboard Mir. This was later attributed to a manufacturing defect; they don't normally burn with an open flame.

designbot, I think TJH's second comment on 5-pound tanks suggests he meant Why don't miners carry a larger oxygen tank?

In any case, the CO problem definitely overwhelmed the oxygen problem. It wasn't a lack of oxygen, it was too much carbon monoxide, which is deadly. It's possible to absorb CO through the skin, and it will quickly find its way into red blood cells which will favor it over oxygen and displace the blood's ability to supply oxygen to the body and brain.

It would seem the operative question isn't that of oxygen supply, but protective measures against CO-impregnated air. It may indeed be nearly impossible to mitigate against this danger.

By: dhartung

dhartung — Fri, 06 Jan 2006 04:22:16 -0800

I should clarify: there may be little that can be done for miners already trapped in a CO-saturated airspace.

Since it appears that the Sago mine had "substantial ventilation, roof control, and emergency escape violations", however, the mitigation would seem to be more effective in the prevention arena.

By: rollbiz

rollbiz — Fri, 06 Jan 2006 17:08:21 -0800

A single tank, the size fire-fighters use, lasts between 30 and 45 minutes. It's possible to wear two, but one + mask and regulator is very tiring to work in.

Not that it would've mattered over days, but when I went to the firefighting academy they taught us breathing strategies that coupled with dormancy would allow you to stretch an SCBA tank for 2-4 hours, as opposed to 45-60 minutes in normal activity or 20-40 minutes under stress and high activity. I wonder how controlled breathing techniques would work with a machine like this.