EN 136 - standard full face masks EN136 Full Face MasksThis standard specifies the requirements for full face masks for use as part of a respiratory protective device. These facepieces may be used in negative pressure systems, powered or supplied air systems .There are three classes of Full Face Masks:Class 1 – Light duty and Low maintenanceClass 2 – General duty, with maintainable partsClass 3 – Heavy duty Fire fighters