Purify Air can help the adventurer move swiftly and without distractions as much as would be otherwise from a gas or similar cloud. Whatever CM related boosts are in place now are massively increased. The effectiveness of the defensive bolstering would be at least equivalent to Mobiles when specifically against clouds.

In addition to this, when there is no cloud even in the room the spell will give a +1 per round boost to regeneration of HP from the invigoration of the system biologically/magically and a +1 *to CS*/+5 to Mental CS Circles. The mental acuity and manna related focus is increased with the purification of the respiratory system such that the mind is able to receive more oxygen and general focus, hence the CS bonus.

Purify Air would become a totally different spell that would be one of the most requested of Major Spirit casters if the CS boost/health boost was able to be cast on others, for the huge boost to defense against clouds.