Hard drives are a cost effective medium for storing files, but unfortunately there is the risk that they may potentially fail. Depending on the failure of the drive it is possible to recover the data, but this recovery process may need to take place in a Class 100 (or ISO Class 5) cleanroom.
Most people associate cleanrooms with the production of pharmaceuticals or a viral out break. Due to the sensitive nature of the hard drive, they need to be worked on in a cleanroom. Depending on the degree of damage to the hard drive the operators may be able to repair the mechanical parts of the drive in the cleanroom.
It is critical that once the hard drive is opened from the sealed protective casing, it is done in a pure environment. Class 100 cleanrooms are constructed by cleanroom manufacturers to ensure that a concentration of airborne particles (no larger than .5 micrometers) does not exceed a count of 100 per cubic foot of air. Particles are extremely small and cannot be seen with the naked eye. It is possible that dust or other contaminates could become stuck in between the hard drive platters or against the read/write heads.
Data recovery is just another one of many practical examples of how cleanrooms benefit society.