A specially constructed enclosed area, which is environmentally controlled with respect to airborne particulates, temperature, humidity, air pressure, air flow patterns, air motion, vibration, noise, viable (living) organisms, and lighting is defined as CLEAN ROOM.
The purpose of the clean room air-conditioning system is to supply airflow in sufficient volume and cleanliness to support the cleanliness rating of the room. Air is introduced into the clean room in a manner to prevent stagnant areas where particles could accumulate. The air must also be conditioned to meet the clean room temperature and humidity requirements. In addition, enough conditioned makeup air must be introduced to maintain the specified positive pressurization.
On the basis of the method of air flow or ventilation in the clean room, the clean rooms are differentiated into following two types
- Laminar air flow clean room
- Turbulent air flow clean room
Laminar Air Flow Clean Room; air flow pattern is in one direction, that may either be horizontal or vertical at a uniform speed of between 60 to 90 ft/minutes and throughout the entire space.
Figure no.1; showing the laminar air flow
When there is no obstruction to the airflow, removal of conta
mination occurs faster, but when there are obstructions, these obstructions cause the laminar air flow to be turned into turbulent air flow around the obstructions. Then this turbulent area formed got established with higher contamination concentrations. The cleanliness of a laminar air flow clean room is directly proportional to the air velocity.
Turbulent air flow clean room; the general method of ventilation is similar to that found in buildings such as living areas such as offices schools and malls, manufacturing plants etc. but a clean room differs from an ordinary ventilated system through the following points
Figure no.2; showing the turbulent air flow.
- Increased air supply; important aspect of particle control. Mainly provided to dilute to an acceptable concentration the contamination produced in the room.
- High efficiency filters; filter the air supply and ensures the removal of small particulates.
- Room pressurization; provided to ensure that untreated air does not pass from dirtier adjacent areas into the clean room.