OT: Your weather? (*not* about GW)

Currently I have one of those Sam's Club specials... medium size squirrel-cage blower sitting on the floor at my office door, pointing upward at about 45°, blowing into my office... putting cool air on the ceiling, then a ceiling fan spreading it around.

NOT a wife-approved solution :-) ...Jim Thompson

No, that's carbon _MONoxide_. The yellow-orange flame indicates incomplete combustion, which makes CO.

CO2 is what triggers your breathing reflex. This is why it's so dangerous to go to altitude with no O2 to breathe - without CO2, your brain doesn't trigger your body to breathe. Once, on a Boy Scout campout, it was terribly cold, but I was using Dad's old military sleeping bag; I wrapped it all around my face and re-breathed my own exhalations. It was nice and cozy until I woke up in the middle of the night with the worst headache I've ever had, before or since.

And CO2 might be "odorless," but have you ever sniffed a freshly poured glass of some bubbly drink? It _hurts_!

Cheers! Rich

Hi Joerg, I just got one at the local hardware store, for about $100. Unfortunately, the puddle quotient is quite high (hence, it sits in the bathroom doorway on vinyl, no carpet!) and it would need the window to be more than a little cracked for good operation. Of course, it is REALLY dry here, but also gets pretty hot too!

Charlie

That reminds me. Some 25 years ago, I had to hand-wind a 3-phase choke for the government-run power company for one of their rural electrification plants. I don't remember the details but the whole thing must have weighed over 50 kilos. I do remember that I used twin 14 swg (12 awg) enamel wire. Even with two assistants, it was tough keeping the wires taut and wrinkle free and the windings even.

One advantage of living in a backward area is that there are fewer regulations to worry about. _I_ was the regulation :-).

AFAIK

garages

ambient

Never

always

Radon is

from

Yep; Fear, Uncertainty and Doubt (FUD) sells well.

=A0 =A0 ...Jim Thompson

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Let's see. About 70 % of air is N2, molecular Wt of 28, about 21 % is O2 molecular Wt of 32, CO molecular Wt is 28. Not enough lighter to much matter, like O2 and CO2 (mWt 44) it can be reasonably be expected to stay pretty well mixed.

Gases at atmospheric pressure are entirely miscible. Gravity starts to matter at ionospheric altitudes, but there's zilch effect of molecular weight at ground level.

This is because the RMS molecular speed is approximately the speed of sound (there's a factor of 1/sqrt(2) or 1/sqrt(3) in there, iirc), and the mean free path (i.e. distance between collisions) is about 10 nanometers.

Cheers

Phil Hobbs

ambient

O2

stay

Not entirely. Check Hydrogen, Helium and methane behavior. See also propane and butane behavior.

I recall differently, mean molecular velocity is about 3 to 4 times the speed of sound. Gas composition can make mean velocity different, see breathing helium and SF6. I thought STP mean free path was about 2 micron. 10nm mean free path sounds about right for water (or most liquids).

Or maybe i am all full of spoons.

The con ad I was trying to remember...

Hydrogen and helium are extreme in having only ~7-14% of the molecular weight of the 29 that roughly represents air. Propane and butane get destroyed in the ozone layer. Released propane and butane are also intially ground-hugging until these gases get warmed to ambient temperature and greatly diluted - after that they fly free.

CFC and other halogenated hydrocarbon molecules heavier than air reach the ozone layer. They get found there, and "smoking gun" reaction products of ozone-destruction-by-organic-chlorine-compounds get found there.

Speed of sound are very different for these two gases. Speed of sound is inverse-proportional to square root of molecular weight, proportional to square root of "specific heat ratio" "K", and roportional to square root of temperature. Does not vary with pressure except for deviations from "ideal gas".

Helium has molecular weight of 4 and specific heat ratio of 5/3. SF6 SF6 has molecular weight of 146 and specific heat ratio almost certainly lower, probably the 9/7 that professors mention as being the usual for polyatomic gases at "room temperature". At this rate, the speed of sound in helium is maybe 6.88 times that in SF6.

People using their voices after inhaling helium also sound notably different than they do when they are breathing air. Air has molecular weight close enough to 29 and specific heat ratio close enough to the 7/5 said to be typical of diatomic gases at room temperature. That makes the speed of sound in helium about 2.94 times that of air.

Trying hydrogen - similar specific heat ratio to that of air at room temperature, 2/29 the molecular weight - speed of sound is about 3.8 times that of air at same temperature, about 8.9 times that of SF6 at same temperature.

Size of atom ballpark (tenths of a nanometer) or "molecule size" (usually a nanometer to a few nanometers) sounds to me right for liquids. A thousand times size of a smallish molecule (1,000 times roughly a nanometer, or ballpark of a micron) sounds to me about right for air.

However, this sounds to me easy to look up...

The Wiki article on "Mean Free Path" mentions 68 nm at atmospheric pressure, looking to me applicable for air.