Surface Supplied Air

[Tekdiver10]

Hey,
I was reading some posts on people using SSA (Surface Supplied Air) for diving and I have herd them say that they can stay down all day with only a tank of gas. Well isnt the air getting compressed as its heading down the hose to you. So you really couldn't stay down all day right, you would probably have to decompress? Sorry for the stupid question, but im getting a little confused.
Thanks

 

[Gary D.]

Depth is the key.

Most SPORT surface supplied air is above 30' so stay as long as you can.

Gary D.

 

[Northeastwrecks]

Even at 30 feet you will eventually reach an NDL and need to decompress.

Moreover, since you will have been down for a relatively long period, your slow tissues will have had a chance to load up, which may make for a long deco.

 

[pipedope]

I have done lots of surface supplied dives.

It was rare to stay down more than about 2 hours at a time as we usually had to refill the gas tank on the compressor and/or the water pump.

To need decompression from 30' you need to be at or near saturation. I don't think you want to stay down that long. My NAUI tables list the NDL for 40' (none listed at 30') is 130 minutes.

There is lots to do that is very shallow.
When you are only 10-15' deep the limits are your own endurance more than anything else.

When surface supplied it is helpful to have a tender on the surface to take care of the equipment, keep the umbilical under control and to be able to help if the diver gets in trouble.
This is real important if using a compressor with a gas engine drive as you sometimes need to reposition so that it doesn't suck exhaust into your breathing air.

 

[Don Burke]

DecoPlanner, which is pretty conservative, calls for a one minute stop at ten feet for going beyond thirty-three minutes at thirty feet.

I had to go beyond six hours to get it to go to two minutes at ten feet.

 

[captain]

U S Navy dive tables does not require decompression stops for any length of dive if the depth does not exceed 33 fsw.

Captain

 

[Bob3]

U S Navy dive tables does not require decompression stops for any length of dive if the depth does not exceed 33 fsw.

Captain

The new version of the USN tables has moved the "unlimited" depth exposure to 20'.
25' has an NDL of 595 minutes, 30' - 405min, 35' - 310min.


Surface air is hard to beat though, 2-3 people can spend the whole day on the bottom (shallow water) for a buck's worth of gasoline.