THE CLEAN ROOM
A clean room is a room in which the concentration of particles hanging in the air is rigourously controlled to minimize it.
The advances in the hard drive technology made the microelectronics players work in clean rooms.
A clean room is a significant asset because it maximizes the chance of recovering the data. However using a clean room is time-consuming (in average, it is 6 times longer to repair a hard drive in a clean room) and expensive (specific equipment, maintenance...).
We do have a class 100 clean room in our premises that limits the concentration of 0,3µm particles to 100 by cubic foot. By comparison, the human eye cannot see particles smaller than 50 µm.