Random Jottings

The water is cold so your biggest risk is from regulator free-flow!

The other day I was getting some air from my mate Toby at http://www.sovereigndiving.co.uk/ and he was getting his air quality checked, why?

Talking with the tester part of it is obvious.......if the compressor is combustion engine driven are there any traces of exhaust fumes (CO and CO2) getting into the air, is there any carry-over of oil and arguably most importantly is the air dry?

Most shops have the first points covered but the moisture level is a big problem and I thought that I would do some notes this year because of the sheer 'wetness' of the winter, it's the second wettest on record. I could talk about the whys and wherefores but lets just accept that there is lots of lying water and this means the ambient relative humidity is much higher than usual, at some 65% rather than the anticipated 45%.

What does this mean for your local dive centre? Well basically the drying filters are lasting a significantly shorter time which means increased costs, so if you see a price hike of 50p a fill be happy it would tend to imply that the centre is regularly checking air quality and changing filters in an appropriate manner.

But what if they aren't checking air quality in accordance with BS12021? The worst thing that can happen is that there is a bit of surface corrosion in cylinders which will get cleaned out at next inspection, sorry no!

Way back in the nineties divers were dying due to free-flows, earlier than this it wasn't the biggest cause of death because divers tended to stay away from cold water and regulators were big chunky pieces of machined brass. However as time passed divers went diving 'earlier' in the year in cold water and dive trips including air travel became more commonplace and big, chunky, heavy reguators were being replaced with lighter models. A couple of companies were at the forefront of this design change and a spate of freeflow incidents and deaths theatened the existance of the companies, as a knee jerk reaction to 'replicate' the old chunky regs large heat-sinks were placed on critical components and the problem 'went away' but behind the scenes various people at the HSE were analysing the quality of any air left after these events or from buddies and the findings made 'orrible reading.

The moisture content of the air in the tanks was so high that it was condensing and freezing within the regulator leading to the free-flow and in all cases it wasn't ice forming around piston springs or diaphragm that was the problem. A BS was written and implemented in 1999 specifying moisture levels and regular 3 month checks, job sorted?

Unfortunatley not and a report was comissioned in 2006 to look very specifically at incidents of free-flows in low ambinet temperature water and unfortunatley the results and conclusions were not good, it was found that in water temperatures of 8degC you could get a freeflow with a full tank at 200psig even if it complied with the BS. If you read my viz report you will see that the current water temperature is......8degC.

In true HSE deathless efficiency the standard was withdarwn, new guidance notes issued and a new standard implemented in 2014 which further lowered the permissible water content.

So what am I trying to say, well most years even 'aged' filters can remove enough moisture to keep your air quality 'ok' but this year its wet, its really wet, so please dive centres must display the air purity certificate please check it and make sure that it is in date, ask when the filters were last changed and don't begrudge any nominal increase in price to cover changing filters on a more frequent basis. Its for your benefit and will hopefully make sure that you don't end up as a statistic!

So guys and gals please check your air and.........

Dive safe!!



Recommended suppliers

Latest Photographs