Abstract: A transfer port facilitates transfer of a material between clean room modules, and/or between a clean room module and a clean box transporter that can travel through the contaminated ambient environment. A transfer port permits transfer of clean material between Class 1 clean rooms without degrading their cleanliness levels. The clean box transporter cars each comprise a small self-propelled clean room with laminar air flow and a HEPA filter. A door on the clean box mates against a similar door on one wall of the clean room module. A seal between a transporter car door and its opening, and a seal between a clean room door and its opening, a pair of seals disposed inside and outside a split line together define a limited contaminated volume. This volume is evacuated and/or flushed with clean gas to remove as much particulate matter as possible.