Air system for sterile areas

Claim 1

IN AN ENCLOSURE DESIGNED TO MAINTAIN A STERILE INTERNAL CONDITION, THE COMBINATION COMPRISING: A DOOR IN ONE WALL OF THE ENCLOSURE; AN AIR INLET FOR THE ENCLOSURE MOUNTED THROUGH ANOTHER WALL OF THE ENCLOSURE, SAID AIR INLET HAVING AIR CLEANING MEANS; A POWER DRIVEN AIR EXHAUST FAN MOUNTED IN A THIRD WALL OF THE ENCLOSURE AND COMMUNICATING WITH THE INTERIOR OF THE ENCLOSURE TO RECEIVE AIR THEREFROM; SAID AIR EXHAUST FAN HAVING A DISCHARGE DUCT; SAID DUCT HAVING BOTH A FIRST PORT DISCHARGING EXTERNALLY OF SAID ENCLOSURE AND A SECOND PORT DISCHARGING INTERNALLY OF SAID ENCLOSURE; MEANS FOR DIRECTING AIR FROM SAID AIR EXHAUST FAN ALTERNATELY TO ONE OF SAID DISCHARGE PORTS, AND DIRECTING MEANS NORMALLY DIRECTING AIR TO SAID FIRST PORT WHEN SAID DOOR IS CLOSED; CONTROL MEANS OPERATED BY SAID DOOR AND CONNECTED TO SAID DIRECTING MEANS AND POSITIONING SAID DIRECTING MEANS TO DIRECT AIR TO SAID SECOND PORT WHEN SAID DOOR IS OPEN TO REDUCE THE MOVEMENT OF AIR INTO SAID ENCLOSURE THROUGH THE DOOR OPENING WHEN SAID DOOR IS OPEN; SAID SECOND PORT BEING A NARROW SLOT ADJACENT ONE END OF SAID DOOR AND EXTENDING SUBSTANTIALLY THE WIDTH OF SAID DOOR.