difference between polycarbon and glass snorkel mask?
108634
Polycarbon is lighter, easier to form in curves, and usually cleaper.\n\nGlass is more durable (difficult to scratch) and can be tempered so that it's won't form dangerous shards if broken.
562841
I thought that navy rebreathers are still pretty  classified, but they do exist.  Officially, they use carbon filters to scrub the carbon dioxide and only work to about 20 ft, officially.  I know that in the 90's there were commercial rebreathers available, but I don't know the company names.
989817
The Nike Mercurial Vapors are good for speed and control. I think they help me trap better. The older vapors are really good and shouldn't be over 100 dollars anymore. I use the Women's Mercurial Vapors FG. They're pretty awesome!
1166673
The only diffetent between the 2 if how accurate they are.\n\nA beaker is designed to be a workmens/womans tool for general use and nothing special in the lab. Although it will mesure to the set level you want as it is a mass produced rough tool, the production line on whats its build to will not have a high degree of acurataly and volumes can vary between + and - 0.5 mls.\n\nA graducated cylinder on the other hand it meant to be a tool for measuring volumes and hence a high degree of accuratly is need, so the prouction line is more strict to control his. A common graduated cylinder has a accurately range of between + 0.2 to -0.2 mls.
1168785
I found the following information on the below sites.\n\nThe Non-Rebreather mask (NRB) are used for patients requiring large quantities of oxygen.  Patients suffering from traumatic injuries or cardiac related illnesses call for the NRB.  The NRB employs a large reservoir that fills while the patient is exhaling.  The exhalate is forced through small holes on the side of the mask.  These holes are sealed while the patient is inhaling, thus preventing outside air from entering. The patient is breathing pure oxygen.  The flow rate for the NRB is 10 to 15 LPM.\n\nEMS*USA Non-Rebreather Mask w/Safety Vent Pedi/Child and Adult
618927
The smaller mesh provides better protection from particals entering the goggels.  They also are stronger than the larger mesh and take higher impacts without crushing.  The downside is the tighter mesh blocks more of your vision than the larger size mesh, as well as blocking venilation a bit more.\n\nIf you can stand the smaller mesh, I'd reccomend it highly.
321271
well, when they make the soda, they inject carbon dioxide (the gas you exhale as a waste-product of respiration) at a pressure of several atmospheres (atmospheres are just a way of measuring pressure, the earth exerts a pressure of 1 atmosphere at sea-level, less pressure above sea-level, and more below it).  So the CO2 (carbon-dioxide) is injected at a pressure several times greater than normal.  CO2 easily dissolves into most liquids at normal atmospheric pressure, but even more so at greater pressures, therefor allowing larger volumes of gas to be dissolved into said liquid (it also dissolves more easily into colder liquids, which is why cold soda has more "fizz" than warmer ones).  Now that the CO2 is in solution, the container is sealed, so the atmospheric pressure is higher than that outside of the container.  When the container is opened, the pressure is equalized, and these large volumes of CO2 come out of solution, forming small bubbles, releasing the CO2 into the air, as the increased atmospheric pressure is no longer present to keep the CO2 in solution.  Now when you drink it, these small bubbles of CO2 hit your tongue, and the actual "taste" of the fizz, is actually a mild burning sensation caused by carbonic acid.  And that is why soda pop fizzes.  On a related side-note, this is in essence what happens to scuba divers who experience decompression sickness, or "the bends".  Gases which are constantly present in our bodies (in this case we are concerned with the nitrogen that is present), exhibit similar properties to CO2.  As the diver descends, he is increased to increasing pressure, much more so than elevation changes on land, since water is many times heavier and denser than air.  As the pressure increases, more and more nitrogen is absorbed and put into solution in the diver's body tissues.  When it comes time for the diver to ascend to the surface, he must do so slowly, if he does not, the effect is similar to what happens when you open a soda.  If he ascends at a normal pace, the nitrogen is easily released, but if he ascends to quickly, the sudden change in pressure causes the nitrogen to be released very rapidly, therefor forming small nitrogen bubbles in the various body tissues.  In effect, he has been opened like a can of soda.  These bubbles can form in any tissue, leading to extreme pain, deformity (if enough bubbles are formed in the bones), paralysis (if enough bubbles are formed in the spinal column or other major nerve clusters), or even death (if enough bubbles form in the brain).  I hope this answers your questions!
826505
Perflurocarbon, maybe? There's one called 'Decalin' that can be breathed by animals in a liquid form.  Or maybe "Perflubron"? That's another breathable liquid that is "similar to plastic teflon. This liquid carries oxygen and carbon dioxiode just as well as air and does not mix with water. Today, Perflubron is only used in medical precedures such as clearing congested lungs and as a blood substitute during surgery. A unique characteristic about this liquid is that it carries the same amount of oxygen as the amount of oxygen in the air in the room it is in."
627978
It depends on what you're willing to pay and the effort you want to put into it.\nI'd always go rubber as it is stronger and more durable.\nLatex would be preferable to PVC.  I just don't think PVC cuts it on skin type things.
642661
Self-Contained Underwater Breathing Apparatus
1158324
the difference is in price. itried both and didnt see any difference. go with gilette fusion. it is great.
357158
Glass or perspex(plastic).Each have their advantages and disadvantages
1087393
SPH means sphere, CYL means cylinder.  Just some instructions about how should the optician cut your glass.
40709
A large glass marble will do the same thing as the magnifying glass, And it is easier to carry around while camping / hiking. (or while your deployed)
407020
I'm not sure what model watch you have.  The best thing would be to take it to a local dive shop and see what they have to say.  I do know that in order to use a computer with Nitrox your computer has to have Nitrox settings.  If your computer doesn't have Nitrox settings you will have to buy what that does.  In order to breath Nitrox you will have to take a class first you can ask about that at the dive shop as well.
22367
A mask is all about the fit.  A perfect fit (strap not too tight, no water leaks -- pereferable even when you laugh or grin) is the only real criteria.  Any mask sold by a reputable shop would fit the bill.\n\nFins -- you need to decide between full foot and open heel.  My preference is open heel (more versatile -- especially for shore diving) although some prefer the full foot.  Fit is also hugely important and if you are shore diving in cold water buy your booties first.  My preference is the Apollo bio fins although there are many excellent choices out there.\n\nIn terms of torch, I think that depends on your application.  I like the Ikelite PCA, the UK SL4 and the small UK pocket light.  These would work for tropical night diving.  Anything brighter will overpower the reef.\n\nFor cold water or cave, you probably need to amp up the power a tad bit and I would look at the more heavy duty rechargeables (including canister lights).\n\nI remain a fan of the Suunto Cobra dive computer but there are *many* other great options.  Start with gas type (nitrox or air only), integration (not air integrated, hose air integaration and hoseless air integration), features and budget and go from there.\n\nTons of choices with regualtors -- start with your budget and diving environement.  I really like the scubapros but there are *many* great choices.  Rodale's Scuba Diving does do periodic gear reviews that are worth a look.\n\nWetsuit is alll about two things:  a) correct thickness for the water temp and your cold tolerance; and b) fit.\n\nWhat about a bc?
223773
Kes is probably correct.  But there's another possible reason.\n\nTempered glass (especially mass produced), is generally less expensive than polycarbonates like lexan.\n\nAlso, polycarbonates are more suceptible to scratching and discoloration.