A clean room and an appropriate extraction system, complete with an ionizer, is enough to guarantee that the air is sufficiently free of particles for hard disk components.
Unfortunately, the replaced electronic system didn't improve things, so the disk was unscrewed and opened up in a clean environment. When doing so, no dust can be allowed to come into contact with the hard disk or the magnetic strips/heads. A clean room is not necessarily needed to accomplish that. Powerful extraction systems and an air ionizer are really all that's required.
An ionizer is required in order to clear the air of foreign particles. The negative ions that are emitted bind these harmful substances, which are then big enough to fall to the floor under normal conditions. However, thanks to the powerful extraction system, they're sucked away from the work surface.
After opening up the drive, CBL checked to see that the disk heads were tilted in the center of the disk. The cam must be moved carefully by hand into its resting position. Normally the heads only get stuck if the hard disk receives a strong blow from above or, with a little bad luck, if the notebook shuts down after it's already been packed up.
It's done: The hard disk is opened up. Don't try this at home; with all likelihood, the hard disk will be damaged by dust particles!