Air showers are designed to quickly and effectively remove particulate prior to entering a cleanroom. The air shower selection criteria allow for high air-flow volume combined with high nozzle velocity, providing optimal operational power and force.
Air Shower Design & Functionality Qualities
Air showers are self-contained air recirculation systems installed at entrances to cleanrooms and other controlled environments. Since people and products are the main sources of cleanroom contamination, these cleanroom entry systems quickly and efficiently remove particulate contaminants from workers or products before they enter a clean space.
How an Air Shower Works
Air showers operate similarly to automated car wash pressure washer systems, utilizing multiple steps throughout the decontamination process. The following cleanroom air shower specifications process details the operational aspects of a cleanroom air shower.
The worker passes through the entry door and a sensor activates interlock magnets, which lock the air shower and cleanroom doors.
Numerous adjustable nozzles blow high-velocity streams of Class 100 filtered air onto the worker.
The high-velocity air creates a flapping effect on clothing which produces a scrubbing action, removing particulates from cleanroom garments.
To ensure all particulates are removed, workers raise their arms and rotate in place.
Indicator lights signal the end of the cleaning cycle, and the cleanroom door opens.
Additionally, it takes four to eight seconds of cleaning time and another two to four seconds for the air shower to purge contaminated air before the worker can exit. Computerized microprocessors control the cleaning and wait times associated with the air shower decontamination process.
Air Shower Design Preparation Procedures
Air showers are the final cleaning step before entering a cleanroom. Prior to entering the air shower, workers put on appropriate cleanroom clothing in a gowning room—either a suit (which covers nearly the entire body) or a gown and cap or hood. Since people are the main source of cleanroom contamination, workers must follow a series of procedures before entering a cleanroom.
This “gowning” process disturbs and releases contaminants from street clothes that can settle onto cleanroom garments. Air showers remove the contaminants. This procedure helps to maintain cleanroom standards and helps to lower operating costs. This procedure helps to maintain cleanroom standards and helps to lower operating costs. The decontamination procedure in the air shower means cleaner air enters the cleanroom, reducing product defects and increasing production yields.
High-Efficiency Cleanroom Air Shower Specifications Increase Productivity While Reducing Operating Costs
Air showers blow high-velocity jets of HEPA-filtered air to remove loose particles from people and products before they enter a cleanroom. This decontamination process means cleaner air enters the cleanroom, reducing product defects and increasing production yields. Additional advantages include longer-lasting cleanroom HEPA (high efficiency particulate air) filters because contaminant loads are lower. The pre-cleaning air shower process also reduces the contamination load of the main cleanroom filtration system, reducing energy consumption and maintenance costs.
Air Shower Selection Criteria Application Guide
Whether the goal is high semiconductor yields or a flawless paint finish, controlled environments are integral to manufacturing processes. Air showers are vital to maintaining the clean environment; they help protect operations from the constant threat of air particulat
e contamination. Some of the industries that directly benefit from proactive air shower design concepts include:
How to Select an Air Shower for Decontamination Purposes?
Decontamination air showers are usually used for cleaning gowned personnel before entering a clean environment. However, they are also used to remove particulates from workers as they leave hazardous work areas and mingle with the general public. Further, an exit decontamination air shower can prevent cross-contamination when moving from one workspace to another.
Cleanroom Air Shower Specification Standards
Important factors to consider when specifying an air shower include effectiveness (power and capacity) and air filtration.
Effectiveness — Power and Capacity
Power and capacity are the major influences on the effectiveness of an air shower. Cleaning power is determined by nozzle velocity: the speed at which air is pushed through the nozzles. It takes high-velocity air to dislodge contaminants; the higher the velocity or cleaning force, the more contaminants are removed. Conversely, capacity is the volume of air circulated in the system. More air volume means faster cleaning and removal of contamination through the filtration and recirculation system.
To specify the most effective air shower, look for one that produces nozzle velocities of 7,800 feet per minute (fpm) and circulates 1,900 cubic feet per minute (cfm) of air. Velocity is measured at the nozzle, and cleaning effectiveness deteriorates as distance from the nozzle increases.
Therefore, air showers should have a high number of air nozzles positioned as close to the worker or product as possible. Ideally these nozzles should be able to be positioned and removed to allow for easy inspection of the high-pressure supply ducts.
Air Filtration
An air shower’s recirculating air filtration systems typically use two sets of filters. The first is a pre-filter for catching the bulk of contaminants. The second is a high-capacity, 99%-efficient HEPA filter.
System blower units are usually mounted in the ceiling. If your facility has height restrictions, make sure the blowers can be mounted on the external wall. For easy routine maintenance, pre-filters should be changed regularly. Replacement filters are economical and easy to change.
Air Shower Design Considerations
Modular air shower designs and configurations accommodate specific requirements for industry, as well as the number of personnel using the cleanroom. Modular cleanroom entry systems also simplify shipping and assembly.
Utilizing a 90-degree design, users enter on one side and exit to the right or left at a 90-degree angle. This allows the air shower, with nozzles on two opposing walls cleans workers with ease. In This configuration has fewer air nozzles than the straight-through design and requires the worker to turn 360 degrees to ensure that they’ve been thoroughly cleansed. Other designs may have double doors or even three doors for entry and exit. Configurations include cart/parts-cleaning air showers, which are used for carts, conveyors, pallets and continuous-part operation. Low-profile air showers accommodate facilities with ceilings less than 96 inches. ADA air showers are sized so a wheelchair can turn around in the air shower.
The number of people that need to enter your cleanroom in each amount of time will have a major impact on the size of the air shower and filtration system that is required. Designs range from single batch systems where one person uses the shower at a time, to tunnel systems for larger groups to pass through quickly. Tunnels are becoming more common because of the amount of cycle time needed for a shift change.
Doors
Like air locks, air showers have entrance and exit doors that cannot be opened at the same time. Workers enter one side and exit on the opposite side. When one door opens, the other door’s magnet energizes, preventing it from opening. During the cleaning cycle, both doors are energized (locked) to prevent anyone entering or leaving before the cycle is completed.
Materials
High-quality air shower shells are constructed of steel and painted with a strong, durable cleanroom-compatible finish. For some medical, pharmaceutical, or extremely wet environments, stainless steel construction is ideal.
Some manufacturers offer economy units made of laminated particleboard. However, this option has major weaknesses, including temperature and humidity fluctuations that can cause delamination. The materials are also easy to damage and susceptible to joint loosening. Any of these conditions may generate particulate or biological contamination.
Air Showers & Cleanroom Options
Clean Air Products offers a full range of air showers, including straight-through, 90-degree, low profile (blower on the side), 3-door, part/cart, tunnel and ADA-compliant configurations. Some of the other types of cleanrooms that Clean Air Products offers includes:
