Tempered-glass lens plate Why use snorkels? Rest or swim with face in water, not wasting cylinder air Features of snorkel large bore How do you know a mask fits? 'Sniff' test Two most important selection factors when buying scuba equipment is? fit and comfort Features you look for in a mask low profile Mask creates air space so your eyes can focus.

What is a reverse block? When air cannot escape from a air space during ascent How do you react to reverse block? Slow/stop ascent and give air time to work its way out As you go deeper you use your air _? faster Why do you wear a mask underwater? Light behaves differently in water than in air, which affects how your eyes focus. Where can you get a squeeze? Ears, sinuses, mask, lungs, teeth How do you equalise air spaces in ears? Blow and squeeze nose, wiggle jaw, swallowing How often should you equalise? Every metre before discomfort What do you do if you feel discomfort? Ascend until discomfort eases, equalise, continue descent slowly Why can't you scuba while sick? Congestion can plug air passages so you can't equalize What is mask equalisation? exhale into mask by nose What does your nose need to be in the mask? To equalize First rule of diving Always breathe continuously What happens if you hold your breath during ascent? Lung over expansion, forces air into bloodstream and chest cavity, leading to paralysis or death. Pressure outside air space is more than pressure inside air space. How do you maintain air volume as you descend? Equalize What is a 'squeeze'? As volume decreases, pressure pushes body tissues inwards toward air space, causing discomfort. 1 bar is what depth? 0m/0ft 2 bar is what depth? 33ft/10m 3 bar is what depth? 66ft/20m 4 bar is what depth? 99ft/30m How is air volume affected when depth is increased? It decreases How is air density affected when depth is increased? It increases What happens if you take an air volume underwater with you in a flexible container or inverted jar? As pressure increases the volume decreases, same air but smaller space. Where are some air spaces located in the body? Ears, sinuses, lungs Do you always feel the pressure in body air spaces? Only if the pressure is different inside and outside the air spaces.

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