New Zealand Gold Prospecting & Metal Detecting Forums Archive

Hi all-instead of washing up I got distracted by watching mad bastards in America dredging under car sized boulders about 25 feet down and it raised a question-how deep can you go and for how long before you have to do stupid stuff like decompression stops?
Does it make a difference using low pressure air as opposed to tanks?

Hi
I asked a few questions my self about wether or not you can get the bends with hooka but dont recall getting a good answer so I just googled it here,s 1 answer

For reference I am an MD who has been a certified diver for over 40 years, plus been active in the field of diving and marine medicine. I have used hooka for over 30 years mostly for boat maintance, but also for some recreational diving. You need to take a SCUBA course--not an on line certification. You need in the water experience.

There are some dangers of hooka--you can get bends if you go over one atmosphere. At 25 or so feet it will be very unusual to have nitrogen bubble type of problems. But you can have air embolism at the shoal depths with rapid ascent. There are also risks of pneumothorax, mediastanial and subcutanious emphysemia due to alveolae in the lung rupture. There is also a risk of carbon monoxide poisoning, so be sure about the exhaust of the gas driven compressor.

Dangers of hooka include the above mentioned air embolus and CO poisoning, entanglement of hoses (including some cases of hoses caught in boat's keels or
running gear). There is also possibility of middle ear injury as in diving situation. You want a reserve tank in line after the compressor. You also should have a pony bottle for emergency breathing if there is an issue with the compressor, or air lines.

With common sense, education and safety precautions hookah diving can be safe and fun. I perfer free diving and SCUBA over hookah, but it is all fun.

Edited by user Wednesday, 15 May 2013 10:22:18 PM(UTC)  | Reason: Not specified

I think i can help here,
I've finished the Padi dive and got certified, so here is an answer - table for the depth and time before you need to decompress:


Goold - Decompression chart and it can tell you exactly how to use it :-)

I use the hooker system on the claim in lewis pass which is of course at altitude
a guy at a dive shop in chch told me I was staying down to long I would only come up when the motor ran out of petrol or caz decided it was time for a coffee then she just turned the motor off one is inclined to come up then
I was diving at about 15 to 20 feet and spending in the summer a good 8 hours under the water a day for 3 days on end
the problem was if one gets the bends at altitude then how do you get air lifted to hospital

now days I spend more time in shallower waters and take more coffee breaks I wear 2 weight belts as well as ankle weights this keeps my feet down and I can spend more time on the bottom without the struggle I also found in a pool with a good flow so as not to get washed out the bottom fix a thick rope at the top end and let it float through the pool gives you something to hold on to
as for the big rocks I have always got a healthy respect for them thinking what would happen if on pinned your foot to the bottom and then your motor runs out of petrol
having said that it is fun watching the trout swim past you at eye level

just be careful out there

sorry to confuse you goldstalker but what i was getting at was it dosnt matter if you use hookah or scuba the same decompression rules apply. nearly all dredging in nz occurs in shallower depths so it will not apply to many however there are a few out there that dredge deep. but id say that if theyre putting up the $$$ for the gear to do it then theyve been at it a while and know what theyre doing.

and yea gotta have a good filter, using another members 8inch dredge a few weeks back the engines oil breather was blowing straight on the intake didnt taste good at all, made a few changes and it algood now, also those T80 filters not the best gotta be carefull of fuel spills, and also should check the internals of compressors if they are aluminium as when it corrodes it makes a white powder and aparently its not the best for your lungs.

yea its only after you go beyond 1 astmosphere (30 or 32 ft) that you start to run into trouble with decompression, thats why the alaskan authorities dont allow dredge permits for over 30ft depth.