mostly oil and also water and dirt.

Sorry, with contaminated I didn't mean with other gasses. The air here
too is regulary tested. But you never know how regulary the shop changes
the filter...
If you're at a shop that only does does air fills, you can't be sure if
the air is clean enough

Lee, your argument may or may not hold up.  I'd think that (within reason)
the size of a filter has more to do with (1) the flow rate it can handle,
and (2) how long it last without cleaning/replacement.  For a occasional
use and realtively low flow rate, a small, personal filter might do as
well or better than the possibly much used (and maybe abused) larger size
shop filter.

.. which reminds me -- my home A/C filters are past due for replacement...

Detroit probably has better diving that Cedar Rapids, but I'm not all
that crazy about going there... I can think of a few places where I
would less rather be than Detroit, but it's pretty close the the bottom
of the list... It apparently has better diving than Cedar Rapids -- at
least when the water is not solid... Than again, I don't believe that
there has been *any* Great White attacks in any of the nearby lakes and
waterways...

I've been stationed in San Diego before and I've dove in SoCal
before... The water is cold, but probably warmer than up here... At the
very least, it doesn't form a solid during the winter...

Don't know about the San Diego area, but in the L.A. area, apartments
were rather expensive even back in 1979 when I lived there... A 3BR
condo in Morepark was renting for $900 per month back then... I would
hate to think what they probably go for these days...

You don't think that a little thing like "no guns allowed" would stop
me from carrying, right?  Remember, I consider such laws immoral and
unconstitutional since they came after the one and only law -- SHALL
NOT BE INFRINGED...

Sounds good -- 2 beers it is... Same payoff clauses as last time --
payoff occurs if we both happen to be in the same general area at the
same time... If Hillary does not win the next presidential election,
you owe me a beer... If Hillary does win, I owe you a beer... No fancy
clauses or anything like you and Reefy kept arguing about -- we'll keep
it nice and simple...

Hey, I'll take a case on that one!

Freezing cold water though......

I'm on my second sensor for my third analyzer.  I took the "test your gas"
lesson seriously, perhaps a lot more seriously than most.  In fact, I
developed my own process for ensuring I know what is in the tank I breathe.
I expect my fills to be checked by the shop.  Any shop that fails to do so
is, in my opinion, a bit too casual about their liability and, therefore,
likely to be a bit too casual about my welfare.  I'm not surprised when the
shop askes me to check the gas too, but don't worry about those that don't.
I would expect the shop's analyzer to read the same for me as it did for
them.  I test every tank when it gets home and, once the gas in it is
confirmed, I remove the shop's sticker and add mine.  I use yellow duct tape
and a Sharpie to indicate the mix, the mod, the pressure and the date of the
test.  When it's time to dive,  I read what I previously wrote, set my
computer for the mix in the tank.  I then remove the duct tape to ensure
that I don't, later, mistake a partially full tank for a full one.  It works
for me . . . usually.

I'm sure I've told you the story about how I got bent, but maybe it will
help if others get a chance to read it too.  It happened three years ago on
my annual liveaboard spearfishing and lobstering trip, the one where I do 6
or 7 dives the first day, 7 dives the second day and 3 or 4 on the way back
to the docks.  I pay additional for 32% from the boat's membrane system.  I
arrived with my tanks full and carefully checked my first 3 or 4 fills
aboard.  All were spot on 32%.  The combination of accurate readings and a
frantic dive schedule combined led me to become complacent.  After all,
there was an analyzer on the gas supply and fully functioning membrane
systems are quite good at hitting the same mix, time after time.  What I
forgot was the human factor.

Sometime around the middle of the second day of diving, I noticed that there
were nitrox and air tanks hooked to whips at the same time.  While it was
possible that the boat had independent systems, I didn't think that was the
case.  Out comes my analyzer to see if there might be a problem.  Sure
enough, the tank I was getting ready to dive was 23% instead of 32%.  So was
the tank I had just finished diving.  As you can imagine, with a 6 or 7 dive
a day schedule, I was running close to my no deco limits on 32%.  I was well
over them on air.  About two hours later, my left elbow started feeling a
bit funny, a day and a half from the nearest recompression chamber.  That's
when I made my second mistake.  The first time I was bent, several years
before, it was my right elbow.  It started the same way and, after a few
hours in the chamber, left no noticable problem.  Surely, this one would be
the same.  I continued to dive, but increased my no deco margin and extended
my safety stops for the remainder of the trip.  My elbow didn't get better,
but it didn't get worse either.  I still figured time would heal any wound.
The day following the trip was the beginning of my wife's only vacation that
year.  Not wanting my mistake to screw her vacation up and still believing
that I would be fine without treatment, I still did not seek any medical
help.

Three years later, my elbow and two fingers on my left hand still give me
occasional discomfort.  It could be a lot worse, but it should have been a
lot better if only:
1. I'd checked my gas before every dive or
2. Insisted on treatment as soon as possible or
3. At least gone for treatment as soon as I was back on shore.

If you're going to be stupid, as I was this time, you have to be tough.

Next Monday, I'm leaving for another spearfishing/lobstering trip.  Just
last week, I went out and got an inflator barb/flow restricter for my
analyzer.  Instead of taking everyting out and testing before I attach my
regulator, I'll put everything together, open the valve and test directly
from the low pressure inflator hose of my regulator.  The current system is
both more accurate and a lot faster than was previously the case.  I don't
need to be any tougher.

Lee