You do not have to worry about the use of air.  It will NOT diesel the strut, in fact air is often used and if you look in the ACS catalog you wil find pumps to boost the air pressure to the pressure required.  That said, nitrogen is the better bet because it has no moisture in it to freeze and cause you problems.  But if you want to you are quite safe with compressed air.
 
Ian B. Crowe
LNC 2  C-FKRO