If a facility supplies Nitrox via P.P. filling then they must have 'clean air'. For those facilities, I can't understand why they would have an issue filling an O2 clean cylinder with air, from the 'clean air' system.
For those only supplying Nitrox via a banked Nitrox supply. I am slightly puzzled why they wouldn't also have a 'clean air' supply. The investment for clean air is minimal when compared to the costs of supplying banked Nitrox.
If they don't have clean air, then if they do fill a cylinder off the dirty air supply, then I can understand them removing the Nitrox banding and O2 clean labelling.
For those that don't supply Nitrox, then it is not entirely surprising that they don't have a clean air supply.
When I started using Nitrox, it wasn't a mainstream gas. Access to 'clean air' was an issue. Now Nitrox is even included in some agencies initial diving qualification. As such clean air is readily available.
Popularity and a demand has changed the industry in the UK. Also, I think the shops didn't liked being listed as a facility that provided 'dirty air' rather than 'clean air'.
We used to have a facility locally, who would provide Nitrox by pp. But they had the stupid rule that they wouldn't fill O2 clean cylinders with (clean) air, if they did they removed the O2 clean label, and the Nitrox banding. Our club stopped using them (- it was only a small percentage of the club who where using Nitrox, but they lost all the business). I can't remember the last time any one I know had a fill from them. I don't know if they still have this policy. But the initial policy cost them business, and has continued to cost them business.
One other option - which if the shop is that inflexible potentially won't help.
We used to carry personal filters. When filling at unknown air stations (e.g. boat compressors), or remote facilities. We fitted our personal filters to the cylinders and filled through the personal filter.
In the last 10 years, or possibly longer, I can't remember an issue in the UK when filling an O2 clean cylinder with air. The impression I get is that the vast majority of those providing gas to divers now by default have 'clean air'.
That includes the boats that have on board compressors. The only thing we double check these days is the availability of Nitrox and H.P. O2 for those using rebreathers.
We dived the Scilly Isles last year. There is NO O2 available on the island other than medical. (No Nitrox, no O2 for CCR.) ALL the air is 'clean air'! (We took prefilled cylinders with Nitrox, that where topped off with air during the week, and spare O2 cylinders for my rebreather.)
Ultimately we changed the industry by choosing who to spend our money with, and word of mouth. Don't use X, they only do dirty air. Use Y they are helpful, and will air top your Nitrox.
