These spiraling columns of air frequently develop in tropical areas close to the equator and are less common at high latitudes. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirl, and steam devil. Tornadoes occur most frequently in North America (particularly in central and southeastern regions of the United States colloquially known as Tornado Alley; the US and Canada have by far the most tornadoes of any countries in the world). Tornados also occur in South Africa, much of Europe (except Spain, most of the Alps, Balkans, and northern Scandinavia), western and eastern Australia, New Zealand, Bangladesh and adjacent eastern India, Japan, Philippines, and southeastern South America (Uruguay and Argentina). Tornadoes can be detected before or as they occur through the use of pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes or debris balls, as well as through the efforts of storm spotters. Tornado rating scales
There are several scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.
They are generally found on the floor and other surfaces, until disturbed (by walking, for example). It could take somewhere between twenty minutes and two hours for dust mites to settle back down out of the air. Dust mites are a nesting species that prefer a dark, warm, and humid climate. They flourish in mattresses, bedding, upholstered furniture, and carpets. Their feces include enzymes that are released upon contact with a moist surface, which can happen when a person inhales, and these enzymes can kill cells within the human body. House dust mites did not become a problem until humans began to use textiles, such as western style blankets and clothing. Furniture
Furniture with wooden or leather surfaces reduces the dust mite population. Bed linen
Hot tumble drying a bed linen for 1 hour will kill 99% of mites therein.Weekly changing the bed linen reduces the risk of exposure to dust mites.Cotton covers not covered with complete mattress covers are very likely to become colonized by bacteria and molds; they must be cleaned periodically (at least every second to third month).