What are the possible consequences otherwise? Wouldn't using a non o2 clean reg also effect it and introduce containments?
No, because the reg doesn't introduce anything into the cylinder. The reason they need the cylinder O2 clean is because when you are partial pressure blending many shops will start with an "empty" cylinder. it will have ambient pressure of course but that's not really a concern unless the ambient air is crap.
Then they will pump in the needed amount of 100% O2 and top that off with air.
While the vast majority of shops probably pump O2-clean air, unless you see their analysis from a lab, you can't guarantee that the shop filling your cylinder with air doesn't have an issue. So when you take it to be partial pressure blended, that shop needs to have some assurance that hydrocarbons haven't been introduced.
If hydrocarbons have been introduced, and they try to rush the PPB, things could get hot. Very hot.
The reality is that after O2 cleaning and VIP, even the shop doing the PPB might have an issue with their compressor and it's not discovered until after they have filled your cylinder.
And the next time you go for a nitrox fill, if they have discovered this, they may want to O2 clean it again.
And for the record, with less than 40% in the cylinder, any reg is fine.
You don't need to worry about O2 clean regs until you start getting over 50% and I didn't worry about it for my personal regs until I started getting above 80%.
That said, every reg I serviced for my customers was done as if it was going to be used with 100%.
Except for those lower-end ones that O2 compatible kits weren't available for.
Then you also have particle impingement that is just as much a danger as hydrocarbons. It happens when a teeny little piece of something hits some other surface or item in the line, such as an O2 bank regulator, valves, cylinder, etc., and causes just a little spark. That little spark then has 100% O2 to feed it in an enclosed area.
