TheUngeek: What kind of car is it? Size and weight matter with pressure.
Any thing over 1000-1200 kg should definitely be over 30psi.
Tyre pressure is all about making sure the contact patch is as big as possible whilst keeping the side wall tight
Gooseybhai: Dont trust the service station guages and always check pressure when the tyre is cold.
( I used to run servo's and most in the industry were tired of continued damage to the 'free air' gear including theft so expenditure on the free air was limited and only when it got really bad / nicked). The public dont care about the free air gear and simply 'drop it on the ground', twist the hose, run over the hose etc etc.
DaveDog: Perhaps it is slightly off topic - but is this Nitrogen fill a waste of time or what?
Never attribute to malice that which is adequately explained by stupidity - Robert J Hanlon