For this size Blast nozzle here is the size and the air required for best performance

NO.850 NOZZLE BORE-1/2″/12.7mm
LENGTH – 235mm
Thread Size-50mm
Inlet Size-32mm
Air Requirement-350/425CFM
Horsepower-hp/(kW) 75/(55.93)

THE AIR REQUIREMENT IS TO ACHIEVE 100 psi AT THE NOZZLE