Evidence of the health utility of exercise has been available since the 1950s. The World Health Organization `WHO` recommendations on improving cardiorespiratory and muscle fitness, bone health and reducing the risk of noncommunicable diseases and depression are now widely adopted by the World Health Organization (WHO): „Adults aged 18 to 64 should engage in at least 150 minutes of medium-intensity aerobic physical activity during the week.“ Some recent models claim to be better than previous ones with the inclusion of „washable“ filters. In general, genuine washable HEPA filters are expensive. A high-quality HEPA filter capable of capturing 99.97% of dust particles with a diameter of 0.3 micron. For comparison, a human hair has a diameter of about 50 to 150 micrometers. Thus, a real HEPA filter effectively captures particles several hundred times smaller than the width of a human hair.  Some manufacturers claim filtering standards such as „HEPA 4“ without specifying its meaning. This relates to their MerV (minimum reporting efficiency value). These assessments are used to assess the ability of an air purifier filter to remove dust from the air as it passes through the filter. MERV is a standard used to measure the overall effectiveness of a filter. The MERV range ranges from 1 to 20 and measures the ability of a filter to eliminate particles from 10 to 0.3 microns. Filters with higher nominal values eliminate not only more particles from the air, but also smaller particles.
HEPA filters are made up of a randomly arranged mat of fibers.  Fibres are generally made up of fiberglass between 0.5 and 2.0 micrometers in diameter. Important factors that influence its functions are the diameter of the fibers, the thickness of the filter and the speed of the surface. The airspace between HEPA filter fibers is generally much larger than 0.3 m. HEPA filters are designed to target a number of particle sizes, unlike 7-filters or membrane filters where particles can pass smaller than holes or pores. These particles are captured by a combination of the following three mechanisms (they are glued to a fiber): a HEPA sachet filter can be used in combination with a pre-filter filter (usually carbon-activated) to extend the life of the more expensive HEPA filter.  In such a structure, the first step in the filtration process consists of prefiltling that removes most dust, hair, PM10 and pollen particles from the air. The second high-quality HEPA filter removes finer particles that escape from the pre-filter. This is the case for handling units.
Over the decades, filters have developed to meet the higher and higher air quality requirements in various high-tech industries, such as aerospace. B, pharmaceutical drug treatment, hospitals, health care, nuclear fuel, nuclear and integrated circuit manufacturing. HEPA was marketed in the 1950s, and the original term became a registered trademark and then a generic term for high-yield filters.  HEPA filters are used in applications that require contamination control, such as the manufacture of hard drives. B, medical equipment, semiconductors, nuclear products, food and pharmaceutical products, as well as in hospitals, households and vehicles.