when diving in depth more than 30 metersfor more than 1/2 hr, why is it necessary to ascend slow, and breathe?

Question

on the way up

Answer 1

You need to do that for any dive done on Scuba, not just to that depth or time period. The purpose is to allow your body time to off gas dissolved nitrogen in a slow, controlled manner. Not in a quick violent uncontrolled one, turning your circulatory system into a foaming mess, capable of killing or at the very least incapacitating you for life.

Answer 2

There are two reasons why you should ascend slowly continuing to breathe (never hold your breath) from every dive where you've been breathing compressed air regardless of the depth or time spent.
1. When you take a breath of air under water, the weight of the water above you compresses that air so that a lot more of it can fit into a smaller space, for instance your lungs. When you ascend toward the surface, the weight of the water decreases and the air expands to take up more space. If you are breathing constantly this is not a problem. But if you are holding your breath, the expanding air has nowhere to go. The resulting pressure on your lungs can cause serious problems (lung overexpansion injuries) as the air tries to escape.
2. The water pressure also compresses nitrogen in the air that you are breathing underwater. This compressed nitrogen is carried to your blood stream and to your tissues. If you ascend too quickly, the nitrogen can expand into bubbles in your blood and tissues (a.k.a. decompression sickness or The Bends). By ascending slowly and carefully you give your body time to remove the compressed nitrogen naturally from your blood through normal circulation and exhalation.

All divers should be certified by a recognized diving agency (PADI, NAUI, SSI, etc. to name a few). The training does not take long and it ensures that every diver is aware of and familiar with the safety measures necessary for safe diving and avoiding pressure related injuries.

Answer 3

To allow your lungs to acclimate to the pressure. Otherwise you develop bubbles in the blood, called the bends and you can die. if you do not ascend slowly you need to go into a pressure chamber so that it can be done in a small closed area.

Answer 4

Because you will get the bends.

Im not going to take a page to explain it, but here is a link.

http://www.emedicinehealth.com/decompression_syndromes_the_bends/article_em.htm

page 2 or the second one down explains it pretty well.

Answer 5

You accumulate nitrogen in the blood which has to dissolve slowly otherwise it will give you the infamous bends.