Drying Desiccant

Discussion in 'Digital Photography' started by Geoff Schultz, Dec 16, 2004.

  1. I recently got an Olympus C-8080 and an Olympus PT-023 housing for it. I've
    always shot 35mm before this. I was suprised to see that the housing came
    with desiccant packs that I assume are to keep the port from fogging.

    My problem is that I live aboard a boat in the Caribbean and I need a way
    to dry out the desiccant packs for re-use. We have an oven, but it doesn't
    get used very often. We also have a microwave. Can one use a microwave to
    dry desiccants, and if so, how?

    -- Geoff
    Geoff Schultz, Dec 16, 2004
    #1
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  2. Geoff Schultz

    Dave Guest

    Yeah, if you don't use the desiccant packs the camera fogs up pretty
    quickly. You can re-use them by drying them out in the oven on low.
    Microwaving them will work, but there's a good chance you'll fry the
    paper before the gel is dry.
    Dave, Dec 16, 2004
    #2
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  3. Geoff Schultz

    Guest

    Some desiccants can't be re-used as the chemical reation caused by
    moisture cannot be reversed by heating (depends on the desiccant used
    of course). This company recommends silica regeneration at 350F:
    http://www.ecompressedair.com/desiccant/silicagel.shtml (at the bottom)
    Microwaving the stuff might damage the paper/plastic/silica faster than
    it heats the water, but it's worth a shot.

    Try your housing w/o the desiccant to see if it fogs up. My housings
    never do, in the humid caribbean or in dry california.

    If you have to buy more here is a nice selection:
    http://www.packexpo.com/ve/35753/main.html

    -lance smith
    , Dec 16, 2004
    #3
  4. In article <>,
    Dave <> wrote:
    >
    >
    >Yeah, if you don't use the desiccant packs the camera fogs up pretty
    >quickly. You can re-use them by drying them out in the oven on low.
    >Microwaving them will work, but there's a good chance you'll fry the
    >paper before the gel is dry.


    Load your housing in a cool, dry, air-conditioned place.

    This prevents the housing from COOLING while it is full of humidity-laden
    air. It is the latter that causes fogging.

    I follow this procedure and have yet to have my housings fog up on me.

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
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    Karl Denninger, Dec 16, 2004
    #4
  5. Geoff Schultz

    Rudy Benner Guest

    "Karl Denninger" <> wrote in message
    news:8emwd.5451$jn.2067@lakeread06...
    >
    > In article <>,
    > Dave <> wrote:
    >>
    >>
    >>Yeah, if you don't use the desiccant packs the camera fogs up pretty
    >>quickly. You can re-use them by drying them out in the oven on low.
    >>Microwaving them will work, but there's a good chance you'll fry the
    >>paper before the gel is dry.

    >
    > Load your housing in a cool, dry, air-conditioned place.
    >
    > This prevents the housing from COOLING while it is full of humidity-laden
    > air. It is the latter that causes fogging.
    >
    > I follow this procedure and have yet to have my housings fog up on me.
    >
    > --
    > --
    > Karl Denninger () Internet Consultant & Kids Rights
    > Activist
    > http://www.denninger.net My home on the net - links to everything I do!
    > http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    > http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    > http://genesis3.blogspot.com Musings Of A Sentient Mind


    Two questions.

    Does it help to use dry compressed air from a can to purge the U/W housing
    before closing?
    Where would one go to find suitable desiccant packages.
    Rudy Benner, Dec 16, 2004
    #5
  6. Geoff Schultz

    WebKatz Guest

    Maybe - if you closed the door *real* quick. ;)

    I have my camera in and out of the housing all day, and I'm never near
    any place remotely cool and dry enough to keep the housing from fogging
    up, so I always use a desiccant pack.

    I get the packs from my local pro camera shop for less than a buck a
    pack, and a single pack lasts me about a week if I'm shooting everyday.
    Dave
    WebKatz, Dec 16, 2004
    #6
  7. In article <>,
    Rudy Benner <> wrote:
    >
    >
    >
    >"Karl Denninger" <> wrote in message
    >news:8emwd.5451$jn.2067@lakeread06...
    >>
    >> In article <>,
    >> Dave <> wrote:
    >>>
    >>>
    >>>Yeah, if you don't use the desiccant packs the camera fogs up pretty
    >>>quickly. You can re-use them by drying them out in the oven on low.
    >>>Microwaving them will work, but there's a good chance you'll fry the
    >>>paper before the gel is dry.

    >>
    >> Load your housing in a cool, dry, air-conditioned place.
    >>
    >> This prevents the housing from COOLING while it is full of humidity-laden
    >> air. It is the latter that causes fogging.
    >>
    >> I follow this procedure and have yet to have my housings fog up on me.
    >>
    >> --
    >> --
    >> Karl Denninger () Internet Consultant & Kids Rights
    >> Activist
    >> http://www.denninger.net My home on the net - links to everything I do!
    >> http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    >> http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    >> http://genesis3.blogspot.com Musings Of A Sentient Mind

    >
    >Two questions.
    >
    >Does it help to use dry compressed air from a can to purge the U/W housing
    >before closing?


    Yes. Use your scuba tank. That ought to have a -50F dewpoint.

    >Where would one go to find suitable desiccant packages.


    If you need more than a -50F dewpoint, you've got bigger problems (like the
    water's state being less-than-liquid)

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 16, 2004
    #7
  8. In article <>,
    WebKatz <> wrote:
    >
    >
    >Maybe - if you closed the door *real* quick. ;)
    >
    >I have my camera in and out of the housing all day, and I'm never near
    >any place remotely cool and dry enough to keep the housing from fogging
    >up, so I always use a desiccant pack.
    >
    >I get the packs from my local pro camera shop for less than a buck a
    >pack, and a single pack lasts me about a week if I'm shooting everyday.
    >Dave
    >


    Put a blowgun in your kit, hook to your BC inflator hose, set the housing
    door so that only a crack remains open, and purge it with the tank air.

    You now have a housing full of -50F dewpoint gas; close it up and you're
    golden.

    If that fogs you have bigger problems.

    Think guys and gals - dessicant packs absorb too little water vapor to do
    all that much. Solve the problem by getting the moist air out of the
    housing before you seal it.

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 16, 2004
    #8
  9. Geoff Schultz

    Rudy Benner Guest

    "Karl Denninger" <> wrote in message
    news:Fanwd.5453$jn.125@lakeread06...
    >
    > In article <>,
    > WebKatz <> wrote:
    >>
    >>
    >>Maybe - if you closed the door *real* quick. ;)
    >>
    >>I have my camera in and out of the housing all day, and I'm never near
    >>any place remotely cool and dry enough to keep the housing from fogging
    >>up, so I always use a desiccant pack.
    >>
    >>I get the packs from my local pro camera shop for less than a buck a
    >>pack, and a single pack lasts me about a week if I'm shooting everyday.
    >>Dave
    >>

    >
    > Put a blowgun in your kit, hook to your BC inflator hose, set the housing
    > door so that only a crack remains open, and purge it with the tank air.
    >
    > You now have a housing full of -50F dewpoint gas; close it up and you're
    > golden.
    >
    > If that fogs you have bigger problems.
    >
    > Think guys and gals - dessicant packs absorb too little water vapor to do
    > all that much. Solve the problem by getting the moist air out of the
    > housing before you seal it.
    >
    > --
    > --
    > Karl Denninger () Internet Consultant & Kids Rights
    > Activist
    > http://www.denninger.net My home on the net - links to everything I do!
    > http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    > http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    > http://genesis3.blogspot.com Musings Of A Sentient Mind


    Excellent. I happen to have exactly what you describe already. I think I
    will also pick up a can of that compressed air in a can.
    Rudy Benner, Dec 16, 2004
    #9
  10. Geoff Schultz

    WebKatz Guest

    Actually, the desiccant packs do a great job. I've never had a problem
    with the housing fogging up as long as I use one.
    WebKatz, Dec 16, 2004
    #10
  11. In article <>,
    WebKatz <> wrote:
    >
    >
    >Actually, the desiccant packs do a great job. I've never had a problem
    >with the housing fogging up as long as I use one.


    The dessicant packs are unnecessary and need recharging.

    Purge the housing with tank air and there won't be enough water vapor in the
    housing to fog it.

    The "diving guys" love to sell you crap that's too expensive and solves half
    the problem - especially when you really don't need to buy anything at all.

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 16, 2004
    #11
  12. (Karl Denninger) wrote in news:8emwd.5451$jn.2067
    @lakeread06:

    >
    > In article <>,
    > Dave <> wrote:
    >>
    >>
    >>Yeah, if you don't use the desiccant packs the camera fogs up pretty
    >>quickly. You can re-use them by drying them out in the oven on low.
    >>Microwaving them will work, but there's a good chance you'll fry the
    >>paper before the gel is dry.

    >
    > Load your housing in a cool, dry, air-conditioned place.
    >
    > This prevents the housing from COOLING while it is full of humidity-laden
    > air. It is the latter that causes fogging.
    >
    > I follow this procedure and have yet to have my housings fog up on me.


    I'm aboard a sailboat in the Caribbean without running A/C.

    -- Geoff
    Geoff Schultz, Dec 16, 2004
    #12
  13. In article <Xns95C1AD8AF42DFgeoffschultzorg@216.148.227.77>,
    Geoff Schultz <> wrote:
    >
    >
    > (Karl Denninger) wrote in news:8emwd.5451$jn.2067
    >@lakeread06:
    >
    >>
    >> In article <>,
    >> Dave <> wrote:
    >>>
    >>>
    >>>Yeah, if you don't use the desiccant packs the camera fogs up pretty
    >>>quickly. You can re-use them by drying them out in the oven on low.
    >>>Microwaving them will work, but there's a good chance you'll fry the
    >>>paper before the gel is dry.

    >>
    >> Load your housing in a cool, dry, air-conditioned place.
    >>
    >> This prevents the housing from COOLING while it is full of humidity-laden
    >> air. It is the latter that causes fogging.
    >>
    >> I follow this procedure and have yet to have my housings fog up on me.

    >
    >I'm aboard a sailboat in the Caribbean without running A/C.
    >
    >-- Geoff


    You have a tank full of air with a -50F dewpoint that you're about to
    breathe, right? It happens to be right there, yes?

    (If your tank air is NOT dry, you don't want to be breathing it. It likely
    is full of oil and other not-nice things - as well as moisture!)

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 16, 2004
    #13
  14. Geoff Schultz

    WebKatz Guest

    Nope, not a diver. Not selling anything either. I use the housing for
    snorkling, kayaking, and sailing. No tank = no tank air = need to use a
    dessicant pack. I've tried it without it and everything fogs up in
    about 10 minutes.

    Of course, YMMV ;)
    WebKatz, Dec 16, 2004
    #14
  15. Geoff Schultz

    Dave C Guest

    I've had only rare occurrences of fogging since using desiccant packs,
    AND, in really humid warm weather, injecting some dry air into the
    housing with the camera. A chilling water bath for the housing helps,
    especially if the lens is kept out of the cold water until after the
    housing has cooled. Otherwise, the lens cools much faster than the
    housing walls, so it will get a disproportionate amount of
    condensation. I was even thinking of experimenting with a cover for the
    lens that would insulate it during the first few minutes of a dive,
    allowing the housing walls to cool FIRST. Another project for a
    tinkering fool....

    Being too cheap to BUY desiccant packs, I got several hundred just by
    asking the manager of the shoe department at a discount store to save
    them for me. She was happy to do so, as they were required to remove
    them from shoeboxes that went onto the shelves, presumably so someone
    wouldn't mistake them for food and eat them and bring a lawsuit or
    something. 8^)

    I did some testing and found the desiccant packs could be effectively
    rejuvenated by baking them in an oven at 225 degrees for 3-4 hours if
    laid out on wire mesh racks to promote air circulation. I kept on eye
    on an accurate oven thermometer because the heat cycles sometimes would
    raise the temp up to 240 or more. Hotter tended to fuse the silica gel
    or brown the package wrappers and make them brittle. So, in just one
    afternoon, I rejuvenated several hundred all at once, then sealed them
    up in plastic bags, 10 to a bag.

    If I place two or three rejuvenated desiccant packs in the housing with
    the camera the night before diving, that usually eliminates any
    fogging, even in humid summer conditions (relative humidity of 80% or
    dewpoints in the 60's) and water temps of 50 degrees or so. In worse
    extremes, I've had occasional fogging, but found that could be reduced
    by keeping the housing out of the sun and/or submerging the housing in
    cold water between dives. That was a good suggestion found on this
    group a while back.

    Another thing I tried during those few weeks of hot, humid weather, was
    to always keep the camera in a plastic bag with desiccants. That really
    dried the camera body out pretty well between dive trips.

    Just for giggles, I measured the relative humidity (RH) of scuba tank
    air from my local shop during a hot, humid spell last summer and found
    70% RH from air from a full tank, and as you might expect, 50% RH from
    that same fill when the tank was near empty. During a real hot, humid
    couple of weeks, I was getting some fogging in water temps in the upper
    40's, despite my pre-packing with desiccants, so I tried injecting the
    70% scuba air the night before and had no problem on the next outing.

    To sum up, the desiccants do the trick all by themselves most of the
    time, especially if given some time to work.

    Karl's right about air conditioning, though, as a buddy with air
    conditioning in his house has no fogging and uses no desiccants or
    anything. Of course, if he opens his housing between dives to replace a
    memory card or battery, the more humid ambient air can cause fogging on
    the next dive. That's when the measures above will help.

    Geoff may not have much of a problem in warm water, but if so,
    pre-chilling the housing, but NOT the lens, would probably pull the
    moisture to the housing walls and leave too little to condense on the
    lens once the dive began. That would be an easy practical solution to
    try on his liveaboard situation. That's my guess anyway.

    Dave C

    Source, supplier of unscented, oil-free PURE TALC, compatible with
    drysuit latex seals. If interested, contact
    dcalderbankATcheshireDOTnet, or check eBay listings (eBay ID:
    dave4868). Thanks.
    Dave C, Dec 17, 2004
    #15
  16. In article <>,
    Dave C <> wrote:
    >
    >Just for giggles, I measured the relative humidity (RH) of scuba tank
    >air from my local shop during a hot, humid spell last summer and found
    >70% RH from air from a full tank, and as you might expect, 50% RH from
    >that same fill when the tank was near empty.


    That sucks; you don't want to know what else might be in there.

    Find a new shop.

    My compressor setup (in my garage) produces dewpoints of -70 - -100F on new
    cartridges, and never goes over -50F. The 20% RH indicator turns (at full
    operating pressure!) I change the filters, because they're toast.

    Just in case you don't know, the activated carbon in the filter stack does
    not work once it gets saturated. At all. The consequence of this is that
    you get whatever comes out of the compressor (oil, CO, etc) into your tank
    without filtering once that happens.

    Seriously, your LDS may some day kill you with that gas.

    (BTW, pure unscented talc can be had from any billiard supply store -
    cheaply :))

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 17, 2004
    #16
  17. Geoff Schultz

    Ken Tough Guest

    Karl Denninger <> wrote:

    >Think guys and gals - dessicant packs absorb too little water vapor to do
    >all that much. Solve the problem by getting the moist air out of the
    >housing before you seal it.


    The amount of water in the vapour in the air contained in the space
    around the camera in the housing, is tiny. Less than a few drops
    of liquid water. That's easily absorbed by the dessicant.

    To me, it's easier to use them than to fiddle around trying to fill
    the housing with tank air, and keep little fiddly hoses to fill it
    with, and keep those dry and clean in the dive kit. If I need
    to open the housing on the dive boat, it's easier to do what I
    need to do and shut it quickly again with the dessicant in, than
    to try fill the housing with tank air, potentially when I have
    all my kit on and there's seawater splashing about. But hey,
    if it works for you, great!

    --
    Ken Tough
    Ken Tough, Dec 17, 2004
    #17
  18. In article <JDZBMpHblowBFwf$@objectech.co.uk>,
    Ken Tough <> wrote:
    >
    >
    >Karl Denninger <> wrote:
    >
    >>Think guys and gals - dessicant packs absorb too little water vapor to do
    >>all that much. Solve the problem by getting the moist air out of the
    >>housing before you seal it.

    >
    >The amount of water in the vapour in the air contained in the space
    >around the camera in the housing, is tiny. Less than a few drops
    >of liquid water. That's easily absorbed by the dessicant.
    >
    >To me, it's easier to use them than to fiddle around trying to fill
    >the housing with tank air, and keep little fiddly hoses to fill it
    >with, and keep those dry and clean in the dive kit. If I need
    >to open the housing on the dive boat, it's easier to do what I
    >need to do and shut it quickly again with the dessicant in, than
    >to try fill the housing with tank air, potentially when I have
    >all my kit on and there's seawater splashing about. But hey,
    >if it works for you, great!
    >
    >--
    >Ken Tough


    For day trips I don't open the housing on board. It is loaded and sealed
    before I leave for the trip.

    If I'm on a multi-day trip, it is assumed I have somewhere DRY to do the
    work (if nowhere else, my BUNK!) I'm not opening my housing in a place
    where a mishap will lead to said seawater splashing about.

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 17, 2004
    #18
  19. Geoff Schultz

    Dave C Guest

    Karl Denninger wrote:
    > In article <>,
    > Dave C <> wrote:

    SNIP
    > >70% RH from air from a full tank, and as you might expect, 50% RH

    from
    > >that same fill when the tank was near empty.

    >
    > That sucks; you don't want to know what else might be in there.
    >
    > Find a new shop.
    >
    > My compressor setup (in my garage) produces dewpoints of -70 - -100F

    on new
    > cartridges, and never goes over -50F. The 20% RH indicator turns (at

    full
    > operating pressure!) I change the filters, because they're toast.
    >
    > Just in case you don't know, the activated carbon in the filter stack

    does
    > not work once it gets saturated. At all. The consequence of this is

    that
    > you get whatever comes out of the compressor (oil, CO, etc) into your

    tank
    > without filtering once that happens.
    >
    > Seriously, your LDS may some day kill you with that gas.


    Hi Karl. Let me explain why it might be a little premature to conclude
    the shop or air is no good. I stopped down at my local LDS today to
    pick up some tanks and they were happy to discuss the water vapor
    concern. In fact, they allowed me to copy their recent quarterly
    Certificate of Air Quality testing report, which happened to be done in
    September, with filters that were due for changing shortly thereafter.

    The results indicated that there was no carbon monoxide, no oil, and
    low carbon dioxide (110 ppm), but significantly elevated water vapor
    (120 ppm).

    You know more about air purification than I do, but for the purpose of
    group discussion, here's what the Certificate had to say. It has
    notations about water vapor recommendations, primarily based on it's
    impact on equipment performance. It specifically stated that levels
    above 66 ppm _may_ cause problems with regulator "freeze up" and other
    problems such as SCBA mask fogging, etc. It also stated that those
    higher levels of water vapor _may_ lead to improper air purification,
    which you had stated. Would it be fair to say that the absence of
    carbon monoxide and oil indicate the purification is still
    satisfactory? (Water vapor aside.) I wish I could present a report of
    the shop's air purification _after_ a filter change, which reportedly
    resulted in low levels of water vapor, but I don't have it.

    Also, getting back to the benefit of injecting air into the housing to
    prevent fogging, I tested another mostly empty cylinder today and found
    the relative humidity to be 40%. Let me just mention that my methods
    are simply to place a household humidity gauge (calibrated against a
    similar gauge) into a plastic bag which is purged and filled with tank
    air. I've been assuming that such a gauge is giving reading of relative
    humidity, since the scale is Zero to 100.

    I haven't been able to figure out what I've read about the relationship
    between relative humidity, temperature, and dewpoint, but it's probably
    safe to say that injecting that drier air could make a significant
    difference when conditions are most conducive to fogging. Wouldn't you
    agree?

    I personally don't think Geoff will have any problems with fogging in
    the warm water of the Caribbean, but this one measure would certainly
    be easily accomplished (with precautions to avoid introducing wster
    droplets, etc).

    > (BTW, pure unscented talc can be had from any billiard supply store -


    > cheaply :))


    That's what I had heard, but it turned out not to be true around here
    (NE US). For a couple of years, I had been looking for and unable to
    find pure talc in at least 1-lb amounts at a reasonable cost. I tried
    several pharmacies, about a dozen billiard supply outlets, and numerous
    web searches and found very little out there. Billiard supply outlets
    often didn't carry it, or only had 2 oz bags of pure talc for about $2.
    The one pharmacy that could obtain pure talc, had similar prices.

    I finally found an industrial supplier with various grades of pure
    talc, and chose, from some samples, a finely ground, USP grade pure
    talc that lubricates well and doesn't clump. I purchased the minimum
    amount of _500 lbs_ and hence, the opportunity to sell some of my
    "lifetime supply", because I don't expect to live to age 400! 8^)

    Dave C (Please note- the above email address is defunct)

    Source, supplier of unscented, oil-free PURE TALC, compatible with
    drysuit latex seals. If interested, contact
    dcalderbankATcheshireDOTnet, or check eBay listings (eBay ID:
    dave4868). Thanks.
    Dave C, Dec 17, 2004
    #19
  20. In article <>,
    Dave C <> wrote:
    >
    >Karl Denninger wrote:
    >> In article <>,
    >> Dave C <> wrote:

    >SNIP
    >> >70% RH from air from a full tank, and as you might expect, 50% RH

    >from
    >> >that same fill when the tank was near empty.

    >>
    >> That sucks; you don't want to know what else might be in there.
    >>
    >> Find a new shop.
    >>
    >> My compressor setup (in my garage) produces dewpoints of -70 - -100F

    >on new
    >> cartridges, and never goes over -50F. The 20% RH indicator turns (at

    >full
    >> operating pressure!) I change the filters, because they're toast.
    >>
    >> Just in case you don't know, the activated carbon in the filter stack

    >does
    >> not work once it gets saturated. At all. The consequence of this is

    >that
    >> you get whatever comes out of the compressor (oil, CO, etc) into your

    >tank
    >> without filtering once that happens.
    >>
    >> Seriously, your LDS may some day kill you with that gas.

    >
    >Hi Karl. Let me explain why it might be a little premature to conclude
    >the shop or air is no good. I stopped down at my local LDS today to
    >pick up some tanks and they were happy to discuss the water vapor
    >concern. In fact, they allowed me to copy their recent quarterly
    >Certificate of Air Quality testing report, which happened to be done in
    >September, with filters that were due for changing shortly thereafter.
    >
    >The results indicated that there was no carbon monoxide, no oil, and
    >low carbon dioxide (110 ppm), but significantly elevated water vapor
    >(120 ppm).
    >
    >You know more about air purification than I do, but for the purpose of
    >group discussion, here's what the Certificate had to say. It has
    >notations about water vapor recommendations, primarily based on it's
    >impact on equipment performance. It specifically stated that levels
    >above 66 ppm _may_ cause problems with regulator "freeze up" and other
    >problems such as SCBA mask fogging, etc. It also stated that those
    >higher levels of water vapor _may_ lead to improper air purification,
    >which you had stated. Would it be fair to say that the absence of
    >carbon monoxide and oil indicate the purification is still
    >satisfactory? (Water vapor aside.) I wish I could present a report of
    >the shop's air purification _after_ a filter change, which reportedly
    >resulted in low levels of water vapor, but I don't have it.


    No.

    It means you got lucky. This time.

    Filtration requires dry gas to work.

    When the gas comes out of the compressor, it is supersaturated with water.
    Its the nature of the beast - you take the gas and compress it to 1/200th of
    its original volume, the amount of water that can be held is 1/200th of its
    original holding capability. The rest condenses out.

    The liquid water is removed by the bulk separators before the filter tower
    in a properly designed system. You now have 100% humidity air. That air
    goes into the tower.

    Activated carbon removes the contaminents, and hopcalite converts CO to CO2
    via a catalytic reaction. However, neither works well with relative humidity
    over 40%, and when saturated with water, neither works AT ALL. In fact,
    activated carbon can actually RELEASE contaminents if it gets saturated with
    water! To be effective, both require DRY gas.

    Enter molecular sieve. The purpose of it is to remove the water vapor (not
    liquid water) from the gas, drying the gas so that it has a RH of less than
    40% before it goes throgh the other parts of the filter bank.

    The intelligent operator has some kind of monitor (whether a simple color
    change "eyeball" or an electronic system) that he/she looks at. Filter
    cartridges must be changed before the RH gets to 40% on the output at full
    working pressure of the system.

    If not, then you have basically no filtration for that time.

    Oil is bad, of course, but many compressors produce little oil vapor, since
    most oil is condenses out at the liquid bulk stage.

    What's worse, however, is thermal decomposition products of the oil and
    other similar contaminents. One of those is toluene, which is a truly nasty
    molecule. It produces neurological impairment that is partial-pressure
    related. It, along with other similar chemicals in the volatile organic
    family, is also not tested for in air quality checks! (This is one of the
    substances that kids like to "sniff" intentionally.... same issue here)

    A lot of dead divers with "unknown causes" may actually have been killed by
    cognitive impairment caused by VOCs (volatile organics) - indeed, DAN's
    reports show that roughly 30% of diver deaths are "drowning, root cause
    unknown" in the end analysis.

    High humidity from a fill station is a major red flag - the shop needs to
    fix this and put in place a proactive system for preventing it in the
    future.

    >Also, getting back to the benefit of injecting air into the housing to
    >prevent fogging, I tested another mostly empty cylinder today and found
    >the relative humidity to be 40%. Let me just mention that my methods
    >are simply to place a household humidity gauge (calibrated against a
    >similar gauge) into a plastic bag which is purged and filled with tank
    >air. I've been assuming that such a gauge is giving reading of relative
    >humidity, since the scale is Zero to 100.


    That's far too high. If you're sure you're getting it all out and getting a
    good reading, then I hope that tank isn't steel. The gas inside is almost
    certainly saturated at its working pressure.

    >I haven't been able to figure out what I've read about the relationship
    >between relative humidity, temperature, and dewpoint, but it's probably
    >safe to say that injecting that drier air could make a significant
    >difference when conditions are most conducive to fogging. Wouldn't you
    >agree?


    Yes.

    >> (BTW, pure unscented talc can be had from any billiard supply store -

    >
    >> cheaply :))

    >
    >That's what I had heard, but it turned out not to be true around here
    >(NE US). For a couple of years, I had been looking for and unable to
    >find pure talc in at least 1-lb amounts at a reasonable cost. I tried
    >several pharmacies, about a dozen billiard supply outlets, and numerous
    >web searches and found very little out there. Billiard supply outlets
    >often didn't carry it, or only had 2 oz bags of pure talc for about $2.
    >The one pharmacy that could obtain pure talc, had similar prices.
    >
    >I finally found an industrial supplier with various grades of pure
    >talc, and chose, from some samples, a finely ground, USP grade pure
    >talc that lubricates well and doesn't clump. I purchased the minimum
    >amount of _500 lbs_ and hence, the opportunity to sell some of my
    >"lifetime supply", because I don't expect to live to age 400! 8^)


    LOL! Ok :)

    I had no problem getting a couple of bottles from a billiard supply
    house.... they'll last me a LONG time I suspect; there's quite a bit in
    one can.

    --
    --
    Karl Denninger () Internet Consultant & Kids Rights Activist
    http://www.denninger.net My home on the net - links to everything I do!
    http://scubaforum.org Your UNCENSORED place to talk about DIVING!
    http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME!
    http://genesis3.blogspot.com Musings Of A Sentient Mind
    Karl Denninger, Dec 18, 2004
    #20
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