Hi my daughter asked a question ,why is a snorkel so short . Can I add a length of tube, to the end perhapse 1 mt with some kind of float on the end that is high enough to stop water entering .Good question, what`s the answer .bobt
There is a very good reason a snorkel is the length it is - if it is longer, there will be insufficient gas interchange on breathing in and out, and carbon dioxide will build up in the tube and consequently in the bloodstream. Carbon dioxide suppresses the desire to breathe - problem! Not, I would suggest, a huge problem if one is floating/swimming on the surface for the most part, but might make a diver overstay a trip underwater - possible big problem.
Also, on returning to the surface, the diver usually has sufficient residual air in the lungs to expel water forcefully from the tube on returning to the surface, without the need to raise the head out of the water to breathe. A long tube will successfuly prevent this, and can cause inhalation of seawater with the next breath, from the partially filled tube - yes, I've done that often enough, and it's horrible.
To help with the water in the tube problem - there are some nifty snorkels around with a short extension downwards from the mouthpiece, so when water slops down the tube, a gentle puff will usually clear the tube without too much effort. Snorkelling in choppy water will always let water down the tube, but practice clearing will soon sort out a problem.
PS I've been diving (SCUBA) for many years, and only last year appreciated the ease of surface toddling along a reef in the Bahamas with snorkel gear only!
Yours, a convert! (Till I forgot, submerged, and choked for my pains!)
One very important reaon is that the muscles in your diaphragm which allow you to breathe aren't strong enough to suck air in whan you are more than about a foot under water.
Try it in the bath if you don't believe me, if you sink down so the top of the snorkel is just above the top of the surface it will be very hard to breathe (especially if you go too deep and get a mouth full of water!)
... they stopped fitting the simple valve at the end of the snorkle that prevented you sucking in water if you ducked. Better the occasional splutting gasp to the surface than the risk of being slowly asphixiated.
what if i increase the dia of the tube conected to the short tube and with one of the mouthpieces, which lets you blow out water. and the other end about 8in above the water level .Iam only talking about going down another 12in can it realy be that dangerous . as a kids we use to use a lenght of 1 1/2 dia pipe and try to go down as far as we could it used to do the ears no good though Please note i am listening to your warnings Bob t
did'nt there used to be a kit on the market that allowed you to expell exhaled breath out into the water with a valve on the snorkel mouthpiece so as to prevent the co2 build up in the tube, and if I remember right it allowed you to operate at about 1.5mtr depths....not sure if its the case but it seems to ring abell somewhere....
If you're suggesting increasing the diameter of the snorkel, this will compound the problem, by further increasing the volume of "stale" air you need to breath in before you get to the "fresh" air from the top of the tube. Narrowing the diameter could in theory compensate completely for the effect of lengthening the tube (twice the length, half the cross-sectional area = same volume of air) but will increase the effort required to suck air in and out - though whether this would be significant I don't know without trying.
I wouldn't be too worried about doing the experiment (especially on dry land!). The comment that CO2 suppresses respiration is to my knowledge wrong - CO2 build up in the bloodstream is in fact the main stimulant of respiration. Try breathing in and out into a paper bag - same in principle as a very long snorkel - and you will begin to feel increasing short of breath as the expired CO2 builds up - you'll need to come out to breath air due to feeling short of breath long before you pass out due to lack of oxygen.
Sailing a Corribee
If you extend the length of the snorkel so you go deeper the water pressure on your body would prevent you breathing in, that's why SCUBA gear has a pressure regulator which keeps a fixed differential between the surrounding pressure and the delivery regardless of depth.
"carbon dioxide will build up in the tube and consequently in the bloodstream. Carbon dioxide suppresses the desire to breathe"
Not quite true - Its the build up of CO2 in the blood that stimulates the desire to breath. That's why you should not take lots of deep breaths (hyperventilate) before doing a free dive. It will flush out the residual CO2 from the blood which can/will lead to hypoxia or anoxia (blackout).
and just to answer the original question - apart from the CO2 problem, your diaphragm is not strong enough to overcome the pressure and draw air down more than a couple of foot.
You are of course vilely right - always get these things back to front. Keep breathing at all times, I say, unless actually barefaced down in the wet stuff. Could be why I like an ickle bottle of air strapped to my back.
With some practice it is not too difficult to learn inhaling through the mouth and exhaling through the nose. This ensures that there is a one-way flow of air in and a separate way out for the 'bad air'. The real problem is the water pressure that, since you're not holding your breath (as when free-diving), would try to 'deflate' your lungs very forcibly. To get an idea of the pressures involved, try putting the end of a tube in the water while you blow into the other end. Most people are surprised at how little depth they can push the tube under water AND still be able to blow bubbles out the wet end.