Advice please!
I’m contemplating a St Francis trip at Easter, and am wondering the best approach to possible bad air. I don’t have an oxygen meter.
Do I
(a) buy one, and if so what is recommended? I don’t want to spend a great deal on something that will probably get little use, but equally I don’t want to die in a mine.
(b) rent, beg or borrow one?
(c) Is there any other (eg flame) test that is appropriate?
(d) Will I feel unwell before it gets dangerous?

What are acceptable oxygen levels?

In my experience, you will feel "off" when it starts to take effect. You generally breathe slightly heavier and faster than normal before feeling light headed.

Having seen 9.8% I'd not recommend going that low :o

Not in Sir Francis I'd hasten to add - the one time I went there we had no issues at all.

As John_Smith says, you'll feel it when it starts to take effect. And If you start getting tunnel vision it's time to wish you'd turned back a lot earlier... The other symptoms might include clammy skin, nausea and cognitive problems.

02 levels can drop off very quickly, and atmospheric conditions can affect 02 underground quite drastically.

Bear in mind with Sir Francis it's a long way back, and you're wading through deep water which is more strenuous that walking - so if you do hit a problem it's more serious than a gentle wander back down a dry level.

I wouldn't take any chances myself, if there are genuine reports of low O2 down there see if you can borrow a gas sensor. Better to carry it and not need than not carry it and need it.

Minimum permissible working O2 is 19.5%. I would guess a lot of people used to high altitude or underground in dubious locations (and with no complicating health conditions) would say 16-19% is tolerable. The lower end of that would be equivalent to about 12,000 feet ASL I think.

https://www.raesystems.com/sites/default/files/content/resources/Application-Note-206_Guide-To-Atmospheric-Testing-In-Confined-Spaces_04-06.pdf 

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If you're contemplating going into a mine with known O2 depletion then an O2 meter really is a must-have bit of kit.

Personally, I find that my own physiology in sub-optimal O2 leads to extreme breathlessness and severe lack of energy, requiring frequent rest stops (every few paces) and a sharp exit!

Not something I like/seek to do on a regular basis I hasten to add, and other people's response may differ markedly, with symptoms not excluding unconsciousness, coma and death.

and remember - the plural of 'Anecdote' is not 'data'

MARK

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Ok - meter recommendations? O2 level limits? A lot of the meters seem to have a 2-year operational life - are they in the bin after that or can they be serviced or recalibrated?
Many thanks for the advice!

If you can tolerate some occasional slow progress a Type6 is OK for low O2 warning, should get one for less than £40.

https://www.ebay.co.uk/sch/i.html?_odkw=type+6&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR6.TRC0.A0.H0.TRS0&_nkw=type+6+miners+lamp&_sacat=0 

Hi Pete

See my last earlier post for a link on O2 levels.

I've used a QRAE 4 gas sensor, bought new but much discounted on eBay.

Most models just need an annual calibration, which mostly involves twiddling something while feeding known concentration gases into the device.

Don't use Ribble Enviro. Had dreadful service with them.

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I imagine for television they had to leave when the O2 alarm went off at 19.5%. Because the camera crew and Mr Rose were 'working'

I would personally say that a fit and healthy person could wander around an easy mine all day in 17% and not even notice, other than the pain in their ears from the alarm.

But as we all know things change, if you find yourself having to make a rapid exit crawling in chin deep mud or a complicated SRT pitch it would be a totally different story.

If you know anyone who works anywhere industrial with confined spaces they might be able to 'borrow' one for a weekend.

Last Sunday I was in somewhere with fairly low O2, min 15.4%, a good length of time at ~16.5% and we noticed that we were a bit underpowered and getting out of breath a bit quicker but nothing that made us want to bail out.
The worst bit was the bloody alarm going off all the time and annoying the hell out of me. ;)

From experience, in Blackett Level, if the going is easy you can easily get into bad conditions without noticing any effect. We got down to ~14% without any symptoms. In this situation we could possibly have got into a very bad place before we had registered a problem.

A meter is a really useful tool as it allows you to make an informed decision about whether you want to go on depending on how bad the air quality is and how strenuous the ground is.
Using a lighter is a simple alternative but is more of a Go-NoGo measure, it will let you know that the air is bad but no more than that. In wet conditions, like Sir Francis, regularly trying a lighter without it getting wet is a right pain.

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I was always under the illusion that it was Sir Francis Level. Maybe something to do with the air quality

I have to confess to having looked at the title of this thread and wondering "when was he canonized?"....

As has been said, a proper oxygen meter is your best bet if there are any concerns, a flame will only warn you by going out when there's less than 17% in the air. Although that's a level you can tolerate for quite a while, you don't know how much below that it's getting. Knowing your own physiological response to low levels helps too, but really you need to have been somewhere with an oxygen meter to be able to equate these to actual air quality - I've done this in a number of the shalegate soughs in Derbyshire and been down to around 11% on a number of occasions but it's not something I'd care to do regularly!

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I’m hoping that St Francis is the patron saint of Easter Eggs.....

Once again, many thanks all for some invaluable information. I’ve appalled the mean part of me (most of it) and after some consultation with a supplier have splashed out £75 on a ‘disposable’ - ie 2-year life oxygen meter. He basically said that O2 sensors only last a couple of years anyway. I may get a safety lamp also, or failing that a lighter / candle and if I’m lucky enough to come across a deficient bit of air I can hopefully calibrate out me and the flame!

If anyone needs to borrow said meter going forwards I dare say we can come to some arrangement.

Nice one. I'm quite sure you'll live, and have a great trip to boot :thumbup:

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The worst bit was the bloody alarm going off all the time and annoying the hell out of me. ;)

A strategically placed blob of bluetack can be useful for avoiding the bleeding ears syndrome, all monitors should come with a piece! 😉

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The worst bit was the bloody alarm going off all the time and annoying the hell out of me. ;)

A strategically placed blob of bluetack can be useful for avoiding the bleeding ears syndrome, all monitors should come with a piece! ;D

Hell yes. The real fun is when nearly everybody is carrying one and you've got 6 of them screaming away at the same time!

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Get a canary!

I'm very tempted. A canary and a candle would be quite cool to take down a mine. Bit I still think calibrating both against an oxygen meter is a cunning plan.....

Just come across this. Top of Snowdon (and many others) has less oxygen than the alarm level (if it's ~ 19%)

https://hypoxico.com/altitude-to-oxygen-chart/ 

I'm very tempted. A canary and a candle would be quite cool to take down a mine. Bit I still think calibrating both against an oxygen meter is a cunning plan.....

I've taken a candle and a Jack Russell terrier down a mine, as Simon will recall....

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Just come across this. Top of Snowdon (and many others) has less oxygen than the alarm level (if it's ~ 19%)

https://hypoxico.com/altitude-to-oxygen-chart/ 

Yup 🙂

That has the makings of a Daily Post article if ever I saw one... "Paying tourists exposed to dangerous and illegal oxygen levels".

Somebody should probably do something about it 🙂

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