AP Diving Oxygen Sensor (R22D)

Everybody who owns a rebreather needs to regularly exchange the oxygen sensors, it's just one of those ownership costs that every year you need to spend nearly £200 on sensors. One of the most common rebeather manufacturers are AP Diving with the ubiquitous YBoD frequently seen on dive boats around the UK, obviously AP Diving recommend that you use their sensors, they would, wouldn't they, but what are they like?

A couple of years ago there was a real issue with actually obtaining these sensors as there was an issue in the supply chain. I had an interesting email conversation with AP Diving who claimed that approvals testing was the issue, that was a red-herring (Part of my job is approvals testing of very complex systems) and the supply of sensors eventually started.

I have to say that during the time where you simply couldn't get sensors for love nor money, the feedback from AP Diving was very, very poor. there were lots of promise dates which did not materialise and the main thrust of communications from the company was to 'pre-order sensors from us as other sensors are not fit for purpose', as an engineer I remain unconvinced by their arguments and with a commercial head on still think that the testing was being funded by the pre-orders.

The first batch of sensors which I received from AP looked ok but testing at the dive shop demonstrated that one of the three was defective giving a fixed reading of 0.21, so a 33% failure rate, that's not very good is it? I was lucky that Andy had a cell that worked so at least I was diving, not especially happy but diving!

The feedback from AP Diving on this problem was non-existant despite the dive shop chasing for comments, I guess that they were receiving similar feedback and warranty returns from other Inspiration owners, certainly that was the impression I had talking with other YBoD divers.

This initial batch also displayed a problem in cold water diving with quite a few of the guys doing winter diving out from Eyemouth experiencing a problem where a cell failure was flagged causing the dive to be aborted. In the interest of science I continued through the warnings and when everything warmed up the sensors stabilised and the problem went away. You can do this at 10m and not risk an oxygen toxicity hit but not at depth, but how many people use a rebreather for shallow dives and how many would continue with a deep dive and hope that it all sorts itself out?

So two big problems with the first batch, it was interesting that some guys from Cornwall came up to do some winter diving and claimed not to have seen or heard of the cold water issue, strangely enough in our cold northern climes their problem free units suddenly became problematic!

The second batch I received was problem free, no issues with sensors giving a fixed reading so I must say so far so good, although this reduces the failure rate by half, a rate of 16.5% still isn't very good.

During this time the guys at Narked at 90 sold quite a few of their oxygen sensors and I tried a set and had a few months trouble free diving. It was noticeable that the Na90 guys made no claims that the sensors were a drop in replacement (see below) although personally comparing the sensors side by side there was no physical difference and the outputs with PPO2 from 0.21 to 1.6 were within a reasonable engineering tolerance.

If you decide to use another sensor manufacturer then I would suggest in the short term using the 'odd-ball' as a 4th sensor running to a back-up computer. This will allow you to monitor the performance of the odd-ball sensor and compare it against the AP items. Most guys run a back up computer and this will allow you to gain confidence and ultimately make your own informed decision about which sensors are suitable for your type of diving.

Picture 014
Spot the difference!

Richies ratings 6/10: A consumable product that you 'need' if you dive on a box, it's your choice to look at other products to use on your rebreather, I have and I am happy. Quality problems and poor customer service from AP Diving have caused me significant problems hence my work with other sensors.

Recommended suppliers

Latest Photographs