NSP’s air valve is installed into your board using a Philips No. 2 screwdriver head, this bolt seals the internals of your board from water and dirt ingress. Replace the O-Ring on this bolt if it is damaged in any way or perished. Tighten the bolt by hand until it is firmly tight, but do not over tighten in case of damage.
Contained within your board is air which expands and contracts. This valve must be removed prior to flight travel, as the change in air pressure as the plane increases in altitude can damage your board.