Hello, thanks for your comments.
RoJo - I'll chase up your leads. I think CATS use an Inovent in their vehicles which improves the dosing reliability.
Sean - that's very interesting. Thanks. I'll keep in touch with NWTS off forum - it would be good it we could learn from your exeriences with this vent.
Jeremy - I understand they will be on contract, but thanks for letting me know.

Cheers

Ian Braithwaite
Senior Retrieval Nurse
EMBRACE, Yorkshire