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BBC Watchdog Series: Introduction

Posted on Tuesday December 22 2015 by Admin

Researchers from the BBC’s Watchdog reached out to Chromalytic to assist with one of their investigations. As industry experts in Nitrogen generation, our team were asked to analyse the Nitrogen composition in vehicle tyres.

The feature was conducted to investigate the practice of charging customers for filling tyres with N2 without prior agreement. Not only that but following a breathing air Oxygen test by a concerned and credible member of the public (a qualified diving instructor), it was suspected that (at least some of the time) regular air was being pumped into the tyres - but charged at a premium for the N2 inflation.

The Method

In order to test this further we agreed to check the Oxygen content, and therefore Nitrogen purity, using a combination of a bespoke sampling rig, and our calibrated precision Oxygen Analyser.


Specifically, we built a test box to take a sample of air from the tyre at a preset flow rate and pressure. The pressure determines the flow rate of the sample through the analyser, in conjunction with the flow restrictor.



The system also had a sampling line with a tyre valve adaptor incorporated. Importantly, we fitted means to flush the sample line, test box and analyser with compressed air between tests - giving us a baseline of 20.88% O2. We also fitted a Non-Return Valve immediately after the tyre adaptor - but before the connection to the compressed air flush supply - to ensure that we did not accidentally introduce any air into the tyre.

The BBC investigators obtained a total of 10 tyre samples from various different KwikFit outlets across the UK. 10 new tyres were fitted to KwikFIt onto wheels taken in by the investigators and, on 9 out of 10 samples, a charge was made by KiwkFit for Nitrogen Tyre Inflation. These samples were brought into our workshop for the requested testing (and filming!).  

Want to know the outcome of this investigation? Check out this blog.

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