Charles Hood is seriously impressed by this Suunto trimix computer 
Suunto HelO2 dive computer, £695; £955 with transmitterOver the past 15 years, nitrox has migrated from the world of technical diving into mainstream sport diving. It became the gas of choice as computer manufacturers cottoned on and began offering nitrox devices, making its use relatively simple – the computer works everything out for you.
However the same can’t be said for mixed gas, which has remained in the realm of tekkie diving. Apart from the fact that it is a little more complex to use than simply breathing another gas, trimix, in my opinion, has been held back from being used by advanced sports divers at intermediate depths by the lack of easy-to-use computers and logical planning software. This is a shame because, with proper training, using trimix is, in many ways, far safer than using air at depths below 35m – mainly because you don’t get narked anywhere near as much.
But all this is about to change. Suunto, the Finnish manufacturer that’s renowned for its easy-to-use dive computers, has released the HelO2, a three-gas computer. It has also updated its dive-planning software to Dive Manager 3, which caters for the new mixed-gas algorithms. After several dives with it and canvassing the opinion of divers at Seaways, the BSAC technical diving school in Penryn, Cornwall, I have to say that the combination of computer and planning software is simply staggering.
The HelO2 is really just a grown-up version of its stablemate the Vytec, with the addition of a fourth button, so the menu is similar to the D6 and D9, two other Suunto models. It is supremely easy to use and simple to understand: we managed to set it up, install the software on a Mac running Windows and plan a dive without the use of the manual. It’s just incredible.
The HelO2 can cater for up to eight different gas mixes, including air, nitrox and trimix, with oxygen content of eight to 100 per cent and helium content of up to 92 per cent. The memory logbook function stores dive data in one- to 60-second intervals, and the dive profile can be viewed on the backlit dot-matrix display. It has a maximum depth capability of 120m, but in my view, it is designed for the 40–80m market, complementing the new trimix courses offered by BSAC and other organisations. It uses a new Suunto Reduced Gradient Bubble Model (RGBM) algorithm, which essentially introduces helium to the existing air/nitrox model. Besides this, it gives you all the features you would expect from a dive computer, as well as gas integration via wireless transmitter. Complementing the hardware is the Dive Manager 3 software, which is a delight to use. You simply set up a few parameters, starting with your back gas and decompression cylinder sizes, projected breathing rate and gas reserve percentage. Then you tell it what gas mixes you want to use, and enter the dive depth and bottom time. The software does the rest, calculating your full run time, including stops. It gives you any predicted warnings such as low gas or high pO2, and will even provide gas-blending instructions to give to your filling station. At any time, you can simply tweak any of the parameters and it will recalculate the data.
It is difficult to compare the algorithms of mixed-gas computers as they all require slightly different stop depths and times, so we compared the planning software with similar programs on the market. The run times it provided were generally a few minutes longer than those from the others but were within ten per cent, which is probably as accurate as you can get in this area of decompression theory.
The HelO2 is my product of the year so far – and at under £700, it’s a steal. I advise you to visit your nearest dive shop now and get a demo – you’ll buy it, I guarantee.
DIVE says…
Fantastic – our product of the year so far
Value 10 Performance 10
Contact Suunto • 01420 587272 •
www.suunto.com