desired device as for example a pneumatically operated fastener driving device air tank gauge 30 and pressure regulator valve 31 inform the user of the applied pressure which may be adjusted by a air pressure regulator knob 36 to the desired pressure a bleed valve or air tank drain plug 28 is provided to release air pressure under contingent event of failure or malfunction an unloader pipe 46 extends between the pressure switch assembly 34 and the check valve assembly 26 a pressure release valve 45 is adapted to release air pressure in the assembly should the need arise the compressor assembly may rest on rubber foot pads affixed preferably to the frame structure 22 when the compressor unit is power operated it is operable to provide a source of air under pressure to the reservoir within the frame structure 22 the entire assembly 20 including the frame structure 22 is portable and as shown the frame structure 22 utilizes as a main component thereof elements of tubular stock the tubular elements are connected to define a continuous internal chamber as the frame structure 22 into which air is pumped by the compressor unit 24 and wherein the air may be held as a supply of compressed air turning now to a novel and inventive aspect of the assembly it has been determined that advantageous results may be given to the compressor assembly 20 as a whole if the frame structure 22 is coated in a pvc compound as described herein in a preferred embodiment of the invention the apparatus and method followed to apply the pvc layer to the frame structure 22 includes the following steps a naked frame structure is heated by oven baking for between 5 to 10 minutes in.