The objectives in cleaning a room can vary between industries but the types of contamination that should be removed may be one, two or all of the following types:

A Particles and Fibers
B Chemicals
C Bacteria
D Electrostatic Charges

In all types of Clean Rooms particles and fibers are undesirable although the minimum size of particle which is undesirable will vary. In the electronics and optical industries, very small particles will cause malfunction of the product and in the pharmaceutical and medical devices industries it is thought unwise to introduce particles into the patient.

In all Clean Rooms, spillages of chemicals from one part of the process may be undesirable in another part of the process. The pharmaceutical and medical devices industries are very concerned with bacteria because of the danger to patients but the microelectronics industry is also concerned with bacteria because of their high ion content.

The microelectronics industry is concerned with static electricity because the discharge of very small voltages can destroy silicon chips. Many of the surfaces of Clean Rooms are poor conductors, i.e. plastics, and can develop and retain a high electrostatic charge. It may be necessary to clean these surfaces in such a way as to leave a film of antistatic agent to conduct the charge away.