The Air Purity notice has caused some confusion around divers having scuba cylinders tested and failed, writes Dave Moran.

The Air Purity notice was the result of WorkSafe New Zealand issuing a Hazard Alert on the December 23, 2016.

WorkSafe were once again (first notice issued Dec 11, 2009) bringing to the attention of the dive industry the international concerns regarding cylinders manufactured from aluminium alloy 635, which is known to be used in cylinders manufactured between 1972 and 1988.

This notice was in response to an incident in August 2016, in Sydney, New South Wales, when a Luxfer cylinder ruptured during filling, causing serious injury including a partial amputation of a leg.

Year of manufacture and specification information is stamped in the neck area of a dive cylinder. Typically marked as: MM YY or the DOT special permit (SP), or exemption (E) markings.

WorkSafe have not banned the filling or testing of these cylinders. Note in their notice re: suspected cylinders, they add: “but not limited to” these types of cylinders.

WorkSafe has reinforced good practice procedures for preventing failures. Also noted is that a cylinder’s working life should not exceed 15 years, which is recommended by some cylinder manufacturers.

Dive stores audited by IANZ (International Accreditation New Zealand) have continued to test and fill cylinders that pass IANZ testing procedures. But as many divers have discovered, if they try and have their cylinder filled at a non-IANZ store, their cylinder will not be filled. There is a very strong rumour that WorkSafe will soon issue a Notice advising all auditing agencies to advise their customers (dive stores) not to test or fill certain cylinders.

The cause for these ruptures is mainly due to sustained load cracking – see: Sustained_load_cracking

These cracks develop over time as a result of the cylinder being subjected to high pressures for prolonged periods of time. Many divers have cylinders filled to 3000psi/200bar stored for many months without giving them a second thought.

It is highly recommended, even if your cylinders are not currently identified in the list above, to only store your cylinders with pressure of around 500psi/35bar or less. Do not store your cylinder without any pressure (empty) as this can cause moisture to enter the cylinder.

The oxygen content in your cylinder can also drop below 21% over time due to internal cylinder corrosion. Check your cylinders NOW!