Air blast switch

Air blast switch utilizing a standard 20x6x9 mm microswitch.
You need to add is a rubber membrane 30mm diameter 0,9mm thick (e.g. cut from a bycicle inner tube). Glue that into the ring and glue the little pressure plate onto the membrane to avoid wear.
Glue a hose into the top part of the housing (5 - 6 mm; enlarge hole if necessary)
Use 3mm screws and nuts to fasten housing.

Dependent on the qty of air you blast into the switch you might want to drill a small (very small) hole into the top of the housing to avoid overpressure.
As it is not airtight, it can be used as a surge switch only.