Clean room

Cleanrooms Overview
Typically used in manufacturing or scientific research, a cleanroom has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size.
Cleanrooms are used in practically every industry where small particles can adversely affect the manufacturing process. They vary in size and complexity, and are used extensively in industries such as semiconductor manufacturing, pharmaceuticals, biotech, medical device and life sciences, as well as critical process manufacturing common in aerospace, optics and military.
A cleanroom is any given contained space where provisions are made to reduce particulate contamination and can (if necessary) control other environmental parameters such as temperature, humidity and pressure.
The key component is the High Efficiency Particulate Air (HEPA) filter that is used to trap particles that are 0.3 micron and larger in size. All of the air delivered to a cleanroom passes through HEPA filters, and in some cases where stringent cleanliness performance is necessary, Ultra Low Particulate Air (ULPA) can be used.

Cleanroom Air Flow Principles
Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or multi-directional air flow principles. Laminar, or unidirectional, air flow systems direct filtered air downward in a constant stream. Multi-directional airflow systems are generally used in ISO Class 6 rooms and above whilst uni-directional laminar air flow systems (with 100% ceiling filtration) are typically combined with a ventilated floor to maintain constant, uni-directional flow in ISO Class 4 cleanrooms and better.