Air showers are specialized enclosed antechambers which are incorporated as entryways of

cleanroom A cleanroom or clean room is an engineered space that maintains a very low concentration of airborne particulates. It is well-isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientifi ...

s and other controlled environments to reduce particle

contamination Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, workplace, etc. Types of contamination Within the scien ...

. Air showers utilize high-pressure,

HEPA HEPA (, high efficiency particulate air) filter, also known as a high efficiency particulate arresting filter, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standa ...

- or ULPA- filtered air to remove dust, fibrous lint, and other contaminants from personnel or object surfaces. The forceful "cleansing" of surfaces before entering clean environments reduces the number of airborne particulates introduced. When properly incorporated into cleanroom design, air showers provide an

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

-classified transition vestibule to ensure the cleanliness of the classified cleanroom. Air showers are typically placed between a gowning area and cleanroom; after workers don appropriate garb and

personal protective equipment Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, elect ...

, they enter the shower so that the pressurized air nozzles remove any residual particles from coveralls. Once the program cycle is complete, users exit through a second door into the cleanroom. Air showers (or air tunnels) may also be placed between cleanrooms of different ISO ratings.

Design and functionality

Air showers are generally constructed from cleanroom-compatible

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

materials and feature electronically-powered blowers, filters and high-pressure jet nozzles, the latter being incorporated into the walls and ceiling of the chamber. Air, at velocities of to , continuously streams from the jet nozzles for 30–45 seconds, effectively removing loose

particulate matter Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes defin ...

. Personnel inside the enclosure will lift their arms and turn their bodies for uniform exposure to the air streams, a procedure usually specified in protocol. Air currents from the jets create shearing and

flapping Flapping or tapping, also known as alveolar flapping, intervocalic flapping, or ''t''-voicing, is a phonological process involving a voiced alveolar tap or flap; it is found in many varieties of English, especially North American, Cardiff, Uls ...

forces, which lift and remove contaminants from both flat surfaces and the creases of garments. HEPA filtration within the air shower is capable of removing 99.97% of particles greater than 0.3 μm diameter. Air is channeled within the air shower using a closed-loop system, where it is continuously re-circulated. Air is forced through a motorized filter/blower module into a large plenum, then into the shower through jet nozzles. Particle-laden, contaminated air is routed out of the shower compartment through floor

vent Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal *Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated water ...

s and returned to the filtration unit. This process ensures that only decontaminated air is used to remove particulates from personnel and other equipment, such as supply carts. Often, air showers are equipped with air ionizers to reduce

static electricity Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge. The word "static" is used to differentiate it from electric ...

, as large volumes of high-velocity air create electric charges. Since laboratory equipment, electronic

measuring instrument Instrumentation is a collective term for measuring instruments, used for indicating, measuring, and recording physical quantities. It is also a field of study about the art and science about making measurement instruments, involving the related ...

s and many hi-tech manufactured goods can often be damaged by

electrostatic discharge Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two differently-charged objects when brought close together or when the dielectric between them breaks down, often creating a visible electric spark, spark as ...

, ionizers are essential in rendering material surfaces electrically neutral before entering the cleanroom.

Safety

Interlocking mechanisms are a common air shower feature to prevent both exits from being opened simultaneously, which would allow outside air to enter a tightly controlled environment. This requires occupants to stay inside until the decontamination cycle has been completed. For this reason, safety features such as emergency stops are required by most safety administrations. Alternatively, the air shower may consist of a long

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

not equipped with doors. Personnel slowly walk through to reach the controlled area. Air handling equipment creates an isolated atmosphere using pressure differentials to create fluid boundaries between the inner and outer environments.

External links

Air showers used at NASA

References

{{Reflist Filters Cleanroom technology Rooms