not a bad train of thought... right up until you exceed the LEL...

I'll stick with a bleepy box.

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not a bad train of thought... right up until you exceed the LEL...

I'll stick with a bleepy box.

Remember RULE ONE! If you suspect Methane, stay out.
that's it.
If you have not done some research first the probably nothing is going to help you.

A long time ago, when I started exploring Cornwall's Central Mines, my attention was initially pipped by United and Consols. 2 of the biggest copper mines of the old world, United having an unlined rubbish tip over it. It was always a case of "If you go in united, you've got landfill gas and bio-nasties eating the oxygen, you'll want a safety lamp at least".

Following exploring most of that we then were interested in mines of Scorrier, Wheal Busy, Killifreth and Hallenbeagle. The whole lot are notorious for bad air. Hallenbeagle has raised CO2 from rotting sawdust thrown down shafts and Killifreth and Busy are "thin" largely due to thiobacillus and poor ventilation.

We had a few close ones and my chum and I set about doing some scientific-ish testing.

Armed with this information:-

http://nhvss.org.au/wp-content/publications/CO2.htm 

We set about going into a mine with horrendous low oxygen and "calibrating" everything to everything and ourselves to that. It is quite odd seeing your butane lighter with a 5" flame with the bottom 2" not lit and exploring interfaces of bad air with a flame that stays where it is when you lower your lighter. The mine commonly goes down to 10.4%, which is very very nasty indeed. My Davey lamp dimmed and then went out at 15%, where the butane lighter was quite normal. The lighter started doing funny things until 14% when it made big flashes of flame, but would not light. Lower than 13.5%, the lighter just sparked. Per the table, you'd strike a match and the chemical reaction would happen and the only product was SOx from the match head reaction, no flame at all.

In the meantime, our focus turned to ourselves. I decided that around the 11.2% I would wait, while my chum pushed onto the end of the drive. I was hot, sweaty, feeling weak, but otherwise fine. Following my chum coming back along the drive, he was flushed and "a bit odd". We decided to do some exercise to test how we responded with a bit of exertion. He climbed some stoping (flat) and almost immediately became "drunk". I talked him down and we exited that section back into clean air.

The idea was that we'd calibrate ourselves to our gas meter and know what the numbers meant. I have recently been out with someone with a meter who started freaking out and wanting to turn around at 18%. (When your Davy lamp is quite happy). The whole name of the game is being able to safely explore somewhere without snuffing it. Now, we should all realise that HSE have a very good point and stay at home and watch telly. But since we aren't going to, it follows that we should get ourselves calibrated.

It's pointless carrying a meter if you don't know how the numbers apply to you.

All of this requires more research. The other day, 4 of us did not do an 80m shaft because the O2 was 18% for the bottom third. It's like tuning the engine, you alter the size of your valves and the ports are too small, you increase them and you need a different camshaft, or carburettors. The whole thing has many sets of variables, of which your body has many. The volume of air, your progression through it and how your body functions in a hypoxic atmosphere are huge variables. The same shaft that we chose not to drop was done by 3 people with a starting reading of 20.1%. When they exited, the last reading was 17%. This is quite low. Things start getting interesting around the 13% mark, which is what 4 of us would have probably done to the air in there. It's quite possible that a reduced efficiency and increased exertion would have upped the CO2 and stripped even more O2 making things even more borderline. It's unlikely anyone would have snuffed it, but they would have almost certainly had a "nasty" experience. (A nasty experience is the stage before the "I don't think we're getting out of here alive" experience - both of which are horrible, but not fatal)

As I've said, old cavers didn't have gas meters. They pushed it, they took it slowly and they knew when it was time to turn around. Perhaps they used their carbide lamps, perhaps they used a fag, or lighter, or davy lamp. The important thing was that since they took it steady, they had plenty of reserve oxygen in their tissue fluids. Their bodies changed gradually enough for them to get out. This is what people need to do.

It seems that many people go steaming around mines with their cameras out, looking for those photos to put on facebook, not really seeing what's around them, not really understanding their surroundings, or how their body behaves in them. It's easy to have another gadget for that task, and let that do the thinking for you.

I am about to get another meter. I don't need it for going in levels. I'm fine with that. What I'm not fine with is dropping a shaft with no air in it, or a small shaft that a load of us plan to go down. In this case, a meter is a good thing.

A word of warning. The last close one I had, we dropped the shaft with a meter and decided to leave the meter at the shaft so we wouldn't get scared by the numbers. On route along a big level towards the sound of a massive waterfall, I said "Hang on a sec, light your lighter Kev" to a mate. He had a wet thumb and we carried on towards the sound of rushing water (which indicates good air, right). We got to a shaft station and realised the oxygen was borderline. Like really borderline.

I don't think anything beats proceeding carefully. Effective exploration happens when you personally know when it's time to get out, not because a meter says so.

Do not underestimate the effect of oxygen in tissue fluids. This is fitness and muscle mass related. Small things run out of oxygen first, but use less for starters! I decided that since at 10.2, the table says I'm going to black out, that I'd see whether that was the case. In our industrial unit, we had some big 1600L plastic bags. I rigged one up to some racking and got my other half to tape me into this when it was blown up, along with my gas meter. I rigged this so that if I blacked out, it would rip a hole in the bag and I would regain consciousness. It wasn't like Hutchence, because no whanking was involved.

Anyway, I breathed it down to 6% O2 on the meter and I was still going. This indicated the tissue fluid phenomena. If someone who was anorexic did this, they might have had a different experience!

Again, this is another indicator of numbers on a gas meter being not representative of whether you're about to snuff it, or not.

A couple of years ago I was doing some maintenance work on a 40Mw gas furnace at Tata Steel in Corby. The control valves and thermocouple cables we were working on are located in tunnels below the furnace so, being a confined space we had a multi gas detector which was clipped to Tom's belt.
On returning to the control room to check the thermocouple signals were O.K. he farted - followed about a second later by a mass of sirens and flashing lights from then Crowcon. At least I suppose that proved the methane sensor. Can't remember if it got H2S as well.

There's also a significant proportion of hydrogen in farts, which is why they're so easy to set afire...if only that could be captured...

https://en.wikipedia.org/wiki/Flatulence#Production.2C_composition.2C_and_smell 

This is an interesting and useful thread, it would be good if it did not degenerate into bollocks. :flowers:

The chap I was doing this mucking around with was a medical doc. The next step was to repeat all of the previous experiments, but directly measure arterial oxygen saturation. At this point he became a dad and stopped flirting with death. A correlation of those numbers with numbers from people suffering altitude sickness and various circulatory problems would have completed the picture.

From what I remember, there is a "sensor" on the aorta which detects the blood conc of CO2 and breathing rate is goverened by this. So, when your lung function is impaired, it's the equivalent of going into a low OX, High CO2 atmosphere. IIRC, people who have impaired lung function have a physiological change which governs the rate of their breathing. I can't remember what it is. There is a big picture regarding fitness, mass, oxygen conc and physiological response. A gas meter merely measures one tiny aspect of this.

I would have liked to complete the study. In fact, I'm going to email him and see if he's up for it. It would be something that everyone would find hugely interesting.

After a lot of investigation I am probably going to get a BW Gas Alert Extreme (BW are part of Honeywell) which isn't dependant on having an expensive computer link for the intended adjustment of trigger points and is a bit cheaper than a disposable with the link.
The running cost is much the same as a disposable but the functionality is better. It also has a datalogging capacity, though that does require a computer link, though how useful that is against noting levels down at the time is dubious. There's also the possibility of extending the sensor life by storing it in an oxygen depleted atmosphere, still investigating that.
There are deals on 4 gas units on fleabay but I would rather have something I know the provenance of and I'm not so keen on the upkeep cost of a more complex beastie.
For what it's worth I am planning on using it as a supplement to how I am feeling and not just blindly following the gadget in the way some people do with their GPS units 🙂

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If you do go for one could you post a review here please.

There's also the possibility of extending the sensor life by storing it in an oxygen depleted atmosphere, still investigating that.

small bottle of argon for a mig welder

heavier than air so 'pour' into an airtight box with the detector, which should displace the air and then stick the lid on

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The combustion analyser we used at Tata Steel (a Land Combustion product) used a sensor manufactured by City Technology. I know the Land engineers reckoned many oxygen analysers used their sensors. If you look on the City Technology website they seem to have a sensor with a life of 5 years in air.
Another analyser we had (Servomex) used a paramagnetic system and so had no chemical type sensor with a finite life.

Nick

Have you thought of a canary? Good old fashioned technology, no batteries but just needs seed!

They don't die just pass out and soon recover when oxygen returns.

Roy

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im a huge fan of the eccles lamps now after a year of use on various coal mines on the south wales field the lamp has kept me alive. become accustomed to reading the flame to the point i can work an O2 percentage and then confirm it against my butty's 4gas and was within a 1% of what the 4gas said. plus in the winter crank the flame up on walk back and use the bonnet to warm yours hands on no 4gas can do that

Thanks for that Dave.:thumbsup:
It shows what can come with experience and training.

The ones I worry about are those buying a lamp or gas monitor off E-bay and believing that's all they need to enter dangerous places the next day;(.

Thanks for that Dave.:thumbsup:
It shows what can come with experience and training.

The ones I worry about are those buying a lamp or gas monitor off E-bay and believing that's all they need to enter dangerous places the next day;(.

used the NCB flame card and a ciggy lighter for working out methane levels and getting used to reading the flame cap in relation to the percentage methane levels. and the oxygen you just use a bigger flame than detecting flams and you get used to the way the flame reacts and gets smaller due to lower o2. one of the main reasons i like flame safety lamps is cost effective with the 4 gas the 6 monthly cal cert and the cost of replacing sensors is the reason i prefer the eccles. plus ive noticed that with the 4gas most people dont take readings from the roof level and just have it clipped to a belt rather than following the guidelines in NCB deputies book of taking readings from floor and roof to get a accurate guage of what the air is doing

Some might think it silly but

That deputies book was written with the blood of many miners who lost their lives before lessons were learnt.

To be fair, most of us aren't gas monitoring on a commercial basis so roof and floor readings, while useful aren't the be all and end all. That said, once the alarm(s) trip, it is probably sensible to measure those locations to give a measure of the place.

I appreciate that an experienced user of an Eccles lamp can determine the Oxygen and Methane levels to a reasonably accurate level. For me there are 2 significant downsides, the time required to get the experience and, the primary issue in my case, the practicalities of a lamp in a crawly, wet environment.
My oxygen sensor requires no training beyond how to turn it on and set the trip point, it can be stowed in a waterproof container in those extremely damp places and will work straight away when removed from it. Yes it needs calibrating and the sensor replacing every couple of years but that is, to me, a price worth paying.
Buying something off ebay or the like and expecting it to be accurate straight away is another issue...

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How low can the oxygen level go before Eccles lamps go out?

The ones I worry about are the people who venture into a mine using a flame safety lamp, electronic device, magic crystals, candle, whatever ... stating 'it's never let me down yet', get it wrong and then someone else is expected to go in and drag their lifeless pelt out.

Why not double up ... a gas detector and a flame safety device should do it.

btw I see that some waxes (the fuel in candles) have impurities that supply some of the oxygen to the flame. What I can't work out is if that affects its burning in low oxygen situations.:o

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How low can the oxygen level go before Eccles lamps go out?

... some waxes (the fuel in candles) have impurities that supply some of the oxygen to the flame. What I can't work out is if that affects its burning in low oxygen situations.:o

Every fuel has a different Lower Combustion Limit, viz, an O2 level below which combustion is not supported. This varies between fuels, and also varies for a given fuel depending on the composition of the atmosphere. 'Pure' air gives a lower LCL [fuel will burn at lower %O2] than air which is contaminated with CO2 for example.

CO2 suppresses flame propagation by absorbing heat from the combustion reaction.

I do not have figures to hand for wax, paraffin or naphtha, but n-butane (a C4 paraffin) has a 12% LCL in air, newspaper is 14%; you can add up to a couple of % to each for elevated CO2.

I feel an experiment coming on...

MARK

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