What is "air shower"

n. An extensive cascade of ionized particles formed by the entry of a cosmic ray into the atmosphere

An air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray (i.e. one of extraterrestrial origin) enters the atmosphere. The term cascade means that the incident particle, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, strikes an atom's nucleus in the air so as to produce many energetic hadrons. The unstable hadrons decay in the air speedily into other particles and electromagnetic radiation, which are part of the shower components. The secondary radiation rains down, including x-rays, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons.

The dose from cosmic radiation is largely from muons, neutrons, and electrons, with a dose rate that varies in different parts of the world and based largely on the geomagnetic field, altitude, and solar cycle. The cosmic-radiation dose rate on airplanes is so high that, according to the United Nations UNSCEAR 2000 Report (see links at bottom), airline flight crew workers receive more dose on average than any other worker, including those in nuclear power plants. Airline crews receive more cosmic rays if they routinely work flight routes that take them close to the North or South pole at high altitudes, where this type of radiation is maximal.

The air shower was discovered by Bruno Rossi in 1934. By observing the cosmic ray with the detectors placed apart from each other, Rossi recognized that many particles arrive simultaneously at the detectors. This phenomenon is now called an air shower.

Air shower can refer to the following terms:

• Air shower (physics), the shower of particles produced when a high energy cosmic ray hits an atom high in the atmosphere
• Air shower (room), a specialized antechamber of a cleanroom

Air showers are specialised antechambers which personnel must pass through before entering cleanrooms in order to decontaminate. Decontamination is done by clearing off dust and dirt particles from bodies of cleanroom personnel to minimize contamination of equipment or products.

Designs to an air shower unit include single-side shower, double-side shower, three-side shower, and top shower. Spraying wind speed is around 25 m/s or above through stainless steel nozzles. HEPA filters are generally used to filter out particles greater than 0.3 micrometres in size from the shower air.

Air showers are considered essential equipment in fields where sterile or dust-free conditions are critical, such as life science and biomedical research, pharmaceutical, parenteral drug, microelectronics, aerospace and some precision manufacturing.