What Does Air Shower Mean?
An air shower is a chamber installed between a cleanroom (or other rooms with controlled environments) and the other parts of a facility. It is one of the methods used to prevent the introduction of contaminants into the cleanroom's sterile environment.
The shower itself is a high-velocy, low-pressure, self-contained system that turns on when someone steps into it. The blasts of air remove particulate matter like dusts and flakes from the person, their clothing, and any equipment or item they carry with them.
Safeopedia Explains Air Shower
Air showers can be an essential aspect of facility designs in the pharmaceutical, biomedical, microelectronics, aerospace, nanotechnology, and precision manufacturing industries. All of these involve manufacturing processes that could be compromised by the presence of contaminants.
How an Air Shower Works
The clothing used in a cleanroom is donned in a gowning room before entering the air shower. The garments may be an entire suit or a gown with cap and hood.
To enter the cleanroom, employees have to go through the following process:
- Step into the air shower, activating a sensor that locks the air shower and cleanroom doors
- Adjustable nozzles blow high-velocity streams of Class 100 filtered air
- High-powered air creates a flapping effect on the clothing, removing additional particulates
- The employee raises their arms and rotates in place to allow the air shower to thoroughly clean them
- Indicator lights turn on, signalling the end of the process, and the cleanroom doors open
Working Principle of an Air Shower
The blowers force air through high-efficiency particulate air (HEPA) filters that are 99.99% efficient at removing particles 0.3 microns and larger, and ultra-low particulate air (ULPA) filters that are 99.9995% effective at removing particles of 0.12 microns and larger.
The filtered air enters the chamber at high velocity through the nozzles and disperses particulate matter. The dispersed matter migrates with the air stream towards the lower areas in the chamber where it enters the blower supply plenum through pre-filters installed at its base.
The air is filtered and re-circulated continuously, and since it is a self-contained system, it does not exchange air with its environment.
Efficient Use of Air Showers
With advanced technology, it is now possible to prevent a substantial amount of contaminants from entering a cleanroom. However, to achieve maximum benefit from an air shower to prevent contaminants from entering the cleanroom, certain best practices should be followed:
- The air shower must be properly designed and sized
- It must make use of both HEPA and ULPA filters
- There should be at least 45 seconds of wash downtime in the air shower
- The air supply should be finely filtered to keep the occupant from being bombarded by contaminants
- A fixed nozzle pattern must be followed and preset to direct air in a downward flow
- Sufficient flow should be maintained to achieve a shearing effect and a fluttering of garments to loosen dust
- Cleanroom clothing should be made of materials like nylon, Teflon, and Dacron to prevent shedding
- The pressure inside the air shower must not exceed the pressure outside of it
- The employee must stand in the center and turn around several times during the cycle and position their hands over the head
- The individual must remain in the chamber to allow purge time
- The air shower must be regularly maintained and cleaned