Date: Tue, 02 Jul 1996 22:43:33 -0500
To: cavers@ditell.com
From: "Butch Fralia" sharbu@flash.net
Subject: Air Quality Measurements

I've followed the air quality measurement comments of the
last few Digests with great interest.  Over the last nine
years I've participated in a volunteer cave research project
at a Texas State Park.  Of the 150+ caves on the park, the
majority have some level of measurable CO2 accumulation
ranging from detectable to deadly.  Over the course of this
project, the state has furnished air quality instruments for
our use.  One is an electronic oxygen meter (no longer 
available) and a Draeger device as mentioned by Mark Minton
in Digest 5333.  Using these instruments, we've taken literally
thousands of air quality measurements.

The Draeger instrument was by far the most reliable.  The problem
with the Draeger is the high cost of the tubes, of which one is
expended with each measurement and not reusable.  The Oxygen
meter has a probe that must cleaned often and replaced about 
every three months.  I don't know if later model instruments
have this same problem.  The oxygen meters are calibrated on
the surface at 21% oxygen.  It's easily knocked out of calibration
while moving through tight passage areas.

Unless a caver is involved in a research project such as the one
on the state park, the cheapest and most reliable air quality
instrument available is a BIC lighter.  It can be obtained for
about $0.97 at any convenience store and easily replaced when
damaged or depleted.  It's within the budgetary range of anyone
who can afford to go caving in the first place.  This may sound
like a cop out to the folks who've offered all the fine advice
on air quality instruments but......read on gentle caver!

When caving in the Arbuckle Mountains, the BIC was the air
quality instrument of choice though at the time, no one knew
how reliable or accurate it was at the time.

During the course of the state park project, we became curious
at what oxygen levels the lighter would start reacting.  Using
the instruments we set up a number of controlled experiments and
verified them with a number of repetitions over several years with
different brands.

The lighter will start reacting at 19.5% oxygen.  The flame changes
color and a small gap will begin to be noticeable between the flame
and the jet.  At 18% oxygen, the flame will burn about 1 inch above
the jet.  At 17% oxygen, the lighter goes out and can not be relit.
As mentioned earlier, these measurements were very repeatable and
could be verified by anyone with the instruments to do so.

In our tests, 99% of the time the oxygen was displaced by an equal
amount of CO2, such that 17% oxygen = 4% CO2.  This was not always
the case!  In two caves, the measurements were typically out of 
balance where the CO2 was 2% higher than indicated by the oxygen
level.  This was repeated over years of data!  At the very least,
when the lighter no longer burns, STOP!

I should mention at this point that the physiological effects of
bad air, result from the CO2 rather than oxygen deprivation!  Most
cavers unless they are astmatic (sp?) can tolerate 17% without much
difficulty, they will breath heavier than normal for the amount of
work being performed.  At CO2 levels > 2%, the cave should cave 
slowly!  ESPECIALLY when climbing!  High CO2 will result in a much
higher rate of breathing, the skin will be flushed to pink, and you 
feel hotter than you'd expect in a 68 degree cave.  Hallucination,
panic and even passing out are typical reactions, especially when 
the CO2 level is greater than 4%.  Coming back to the surface,
headaches and even severe nausea may be experienced.  This can be
prevented by stopping in an area that has between 18% to 19% oxygen
for at least 15 minutes before moving on to normal air.  Those of 
us who smoke seem to be able to handle higher levels of CO2 than 
non-smokers since we're used to poor air quality anyway.

If you can afford it and want to play, buy the Draeger for a 
reliable and accurate instrument, otherwise "Flick you BIC!"

Butch