Introduction The pass box is equipment normally installed on the wall between the clean room and any other room. It is used for transfer of material from and into the clean room, without contaminating the air of clean room and without having to open room door. This is achieved with the help of interlocking type doors of pass box. Principal of Working This equipment is installed on the wall between the clean room and the other room. The pass box has two doors at its extreme ends. One door opens in the clean room and other door open in the other room. These doors are electrically interlocked type so that any one door can be opened at a time. This avoids direct flow of air from the clean room to the other room or vice versa. This also obviates the need to open the clean room door frequently for transferring of material from & into the clean room. Thus, it helps in achieving the aim of material transfer without disturbing the cleanliness level of the clean room. Construction The complete body is made of stainless Steel. Each hinged door has wide glass viewing window, through which material kept in the pass box can be seen. These doors are electrically interlocked type, so that any one door can be opened at a time. UV & fluorescent light are a standard feature.