Clean rooms need a lot of air and usually at a controlled temperature and humidity. This means that in most clean room facilities the Air Handling Units (AHU) consume over 60% of all the site power. As a general rule of thumb, the cleaner the cleanroom needs to be, the more air it will need to use. AHU systems can be designed to recirculate (if product characteristics permit) about 80% air through the room, removing particulate contamination as is it generated, whilst keeping the temperature and humidity stable.
In a nutshell a well-designed air handling system should be able to deliver both “fresh” and “recirculated” filtered clean air into the cleanroom in such a way and at a rate so that it flushes the particles from the room. Depending on the nature of the operations, the air taken out of the room is usually recirculated through the air handling system where HEPA filters remove the particulates out of the air.
In some cases the room may encounter high levels of moisture, noxious vapours or gases from the onsite processes, raw materials or products and therefore cannot be recirculated back into the room. When this happened the air in these types of cleanrooms is usually exhausted straight to atmosphere and 100% fresh air is then introduced into the facility.
The volume of air introduced into a cleanroom is often tightly controlled and so is the volume of air that is removed. Most cleanrooms are operated at a higher pressure to the atmosphere, which is achieved by supplying a higher supply volume of air into the cleanroom than the supply of air being removed from the room. The higher pressure then causes air to leak out under the door or through the tiny cracks or gaps that are inevitably in any cleanroom.
Any good air handling system will make sure that air is kept moving throughout the cleanroom. The key to good cleanroom design is the appropriate location of where the air is brought in via the supply and taken out via the exhaust. Although careful design of the cleanroom is important, it still remains that people are one of the biggest contaminants in any cleanroom environment. If a person is just standing still in a clean room they still emit up to 100,000 particles a minute into the clean room environment. Therefore you should try to reduce the amount of exposed skin in any cleanroom environment.
We hope that this article was helpful in helping some of you to understand the basics, necessities and complexity of a cleanroom.
APT Sound Testing provides a comprehensive and proactive cleanroom validation service to the requirements of all current ISO standards and guidelines. If you would like more information on our cleanroom testing services please don’t hesitate to contact Darren directly on 07775623464.