Air curtains

Claim 1

APPARATUS FOR ESTABLISHING ACROSS THE DOOR OPENING OF A COLD ROOM AN AIR BARRIER CONSISTING OF TWO CONTIGUOUS CODIRECTIONAL SUBSTANTIALLY LAMINAR AIR CURTAINS ON THE OUTSIDE OF SAID DOOR FOR THE MAINTENANCE INSIDE SAID ROOM OF A SUBSTANTIALLY CONSTANT ATMOSPHERE OF LOWER HUMIDITY AND TEMPERATURE THAN THE AMBIENT ATMOSPHERE OUTSIDE SAID ROOM, COMPRISING A SELF-CONTAINED DUCT SYSTEM IN THE FORM OF A UNIT ASSEMBLY ATTACHABLE TO THE OUTSIDE OF SAID DOOR OPENING AND PERIPHERALLY EMBRACING THREE SIDES OF SAID DOOR OPENING, SAID DUCT SYSTEM CONSISTING OF A FIRST AIR DISCHARGE DUCT EXTENDING THE LENGTH OF ONE SIDE OF SAID DOOR OPENING AND HAVING AIR DISCHARGE APERTURES ADAPTED TO BLOW A FIRST SUBSTANTIALLY LAMINAR CURTAIN OF AIR ACROSS SAID DOOR OPENING AND, ON THE OPPOSITE SIDE OF SAID DOOR OPENING, PARALLEL TO SAID FIRST AIR DISCHARGE DUCT, AN AIR COLLECTION DUCT LIKEWISE EXTENDING THE LENGTH OF THE SIDE OF SAID DOOR OPENING AND HAVING APERTURES FACING THE AIR DISCHARGE APERTURES OF SAID FIRST AIR DISCHARGE DUCT FOR THE ENTRY THERETHROUGH INTO SAID AIR COLLECTION DUCT OF AIR COMPRISING THE AIR CURTAIN DISCHARGED FROM SAID FIRST AIR DISCHARGE DUCT AFTER HAVING TRAVERSED SAID DOOR OPENING;