Cleanroom Air Filtration
Regardless of cleanliness class, the air to all cleanrooms is filtered through HEPA (High Efficiency Particulate Air) or ULPA (Ultra Low Particulate Air) filters. These filters are rated for 99.99 percent efficiency on 0.3 micron particles (HEPA) and 0.128 micron particles (ULPA). Cleanliness is a function of how much clean air is mixed with the contaminated air in the room. The more clean air, the greater the contaminant dilution, and the higher the level of cleanliness.
Cleanrooms also take advantage of another feature of the filters and that is the pleating of the media in the manufacturing process. This pleating effect causes the air passing through the filter to be delivered in a jet stream. The collective results of these multiple air streams produces a column of clean air moving uniformly away from the filter face.
Cleanroom Temperature Control
The process within the space generally dictates the temperature range that can be tolerated. If there are non-specific requirements, the human factor will usually guide the selection.
Cleanroom Humidity Control
Often overlooked in the design of a cleanroom is the stringent humidity requirement. This can vary, again depending on the process involved. Between 40 to 60 percent is typical with a variation usually not greater than 5 percent.
Walls can be constructed of any non-shedding material that can be wiped down easily and kept clean. Walls can be gypsum board with a seamless coating on metal studs or they can be modular. Modular walls have a tax advantage in they are considered tangible property and can be taken down and moved.
The best cleanroom floors are poured seamless systems, seamless sheet vinyl, epoxy, or vinyl tile in that order. Products that limit dust penetration and can be easily maintained are required.
Most cleanrooms are designed with positive pressure plenums, or ceiling spaces. This requires a special grid system that is usually factory gasketed or it can be a gel system on the more stringent rooms. The grids typically support the HEPA filters, lights, and panels and can weigh as much as 12 pounds per square foot. 12 gauge wire is used to support the grid.
Cleanroom HEPA Filter Units
The heart of any cleanroom design is the filtration that is required. SOme are ducted but the most common are fan powered units. The typical 2’x4′ unit has the capacity of 700 to 800 cfm, with a 1/3 hp motor. Latest designs also include energy efficient watt motors.
Lights are specially constructed for cleanrooms so they are sealed air tight. They also produce heat which must be taken into account. Typical lighting is 70 to 100 foot candles.
While we know what the hardware mentioned above produces in regards to release of microbes, heat, ect. the one element that changes daily is the human element. It has been said that “absolute cleanliness” cannot be maintained with man’s involvement, that robots are the only way to eliminate this source of particulate pollution. Even fully gowned, workers are constantly shedding skin particles. Gowning is required.
Garments can include hair coverings, beard or mouth covering, body covering, shoe covering, and gloves with any combination of the above. Garments should be put on in a gowning room. This gowning room should also be HEPA filtered.
Cleanroom Testing and Certification
Once the room is completed, most specifications call for testing and certification. Some requirements state that the room should be tested annually. Testing is usually conducted by an independent testing agency using the ISO Standards, It is also imperative for the owner to purchase a cleanroom monitor in order to determine the daily status of the room.
Cleanrooms require much consideration, equipment, and supplies. CleanPro®, a division of Production Automation Corporation is dedicated to guiding customers through the design process, set-up, and supply maintenance of cleanroom areas. To get started, send us a request for quote and we will work with you to identify and quote the exact type and class you require. CleanPro works with reputable manufacturers to get you the best materials for your project. CleanPro also carries the furniture and equipment needed to outfit your cleanroom; from storage and gowning to laminar flow workbenches and seating. CleanPro can make your cleanroom functional and efficient.
We have also created a Cleanroom Design Form to help you get started on identifying what type of cleanroom you require.
- Advantages of Modular Hardwall Cleanroom Construction
- Cleanroom Design in 10 Easy Steps
- Cleanroom Operation & Maintenance Protocol
- Gowning Room Design & Protocols
- Guide to Selecting a Particle Counter
- Guide to Cleanroom Certification
- Increasing Productivity & Cost Savings with Air Showers
- ISO14644-1 Cleanroom Standards