Furnish and install a packaged Micro-Filter redundant blower filter/pressurization unit certified by ETL Intertek Testing Services to be in conformance with applicable UL and CSA codes and standards for Class I, Groups C & D, Division I or Class I, Division II, Groups B,C, & D hazardous locations (general purpose optional). The unit shall include stainless steel direct drive redundant pressurization blowers, primary and secondary blower backdraft dampers, internal balance damper, four stages of chemical/particulate filters and remote alarm relay. Unit options shall include air distributor with supply air grille, stainless (galvanized) steel stack shutoff damper/motor.

Provide 30 percent efficient pleated throwaway filters for stages one and three. Provide replaceable media chemical filters for stage two with stainless steel filter cartridges (two) and front/rear access so that filter media can be changed from outside the building using a forklift. Provide HEPA filter for stage four with absolute 99.97 percent efficiency on 0.3 micron particles. Stages two and four shall have a MicroSeal(tm) system to assure 100 percent air filtration with no air by-pass around air filters.

The unit cabinet shall be constructed of 16 gauge galvanized paint grip (optional stainless) steel and coated with two coats of Sherwin-Williams Polane(r) T Polyurethane Enamel.

The unit controls shall include an adjustable stainless steel internal balance damper field set to maintain 0.1 inches of w.c. building pressure to prevent contaminants from entering pressurized area. Exit doors shall have air locks. Provide unit mounted photohelic building pressure switch/gauge, filter pressure drop gauge, explosion proof indicating light for "pressure OK" (green), explosion proof indicating light for "back-up blower on" (amber), time delay relay for normal "door-open" condition, time delay relay for abnormal "back-up fan on" condition, remote alarm relay and explosion proof "off-purge-on" system switch.

The pressurization unit shall be a Model BFPD1400-VS as manufactured by The Birdwell Company in Houston, Texas (no equal). Manufacturer reserves the right to change any product specifications without noticed.