Clean rooms and Dust free environment is a must for Precision Mechanical Engineering. It is not MEMS or nano sizes, even micron sizes accuracy in parts can be affected by Dust and Humidity.
In Electronics, Timepiece Manufacturing, Medical Equipment and Scientific Apparatus companies. Clan Rooms ensure long term reliability and safety of the products not to forget Precision.
EE Design Library - Electronic Product Design Resource.
Even if a Place is partially Dust free, it is better to have all objects with the least surface area. The way Motors are designed, Interiors of houses even a Machine
You can enclose objects with many contours and unclean-able surfaces within a Spherical or Cubical Transparent Cover, this is easy for inspection and cleaning.
Dust, Oil, Sand and Humidity makes Grime. Never allow Rodents and Roaches in the Workplace they are larger than 100 microns.
Resources - Electronic Firms and Electronic Projects.
Tools and Equipment must be maintained free of rust/corrosion and exposure to brine or chemical fumes. Metal tools must be cleaned, oiled and stored in dry places when not in use.