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Smoke screen
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==Infrared smokes== The proliferation of [[Thermography|thermal imaging]] [[Forward-looking infrared|FLIR]] systems on the battlefields necessitates the use of obscurant smokes that are effectively opaque in the [[infrared]] part of electromagnetic spectrum. This kind of obscurant smoke is sometimes referred to as "Visual and Infrared Screening Smoke" (VIRSS).<ref>{{cite book|page=119|url=https://books.google.com/books?id=62VtBQAAQBAJ&q=%22Visual+and+Infrared+Screening+Smoke%22&pg=PA119|title=The Armed Forces of the United Kingdom 2014-2015|first=Charles|last=Hayman|date=10 February 2014|access-date=14 April 2018|publisher=Pen and Sword| isbn=9781783463510 |via=Google Books}}</ref> To achieve this, the particle size and composition of the smokes has to be adjusted. One of the approaches is using an aerosol of burning [[red phosphorus]] particles and [[aluminium]]-coated glass fibers; the infrared emissions of such smoke curtains hides the weaker emissions of colder objects behind it, but the effect is only short-lived. [[soot|Carbon]] (most often [[graphite]]) particles present in the smokes can also serve to absorb the beams of [[laser designator]]s. Yet another possibility is a water [[fog]] sprayed around the vehicle; the presence of large droplets absorbs in infrared band and additionally serves as a countermeasure against [[radar]]s in [[W band|94 GHz]] band. Other materials used as visible/infrared obscurants are micro-pulverized flakes of [[brass]] or [[graphite]], particles of [[titanium dioxide]], or [[terephthalic acid]]. Older systems for production of infrared smoke work as generators of [[aerosol]] of [[dust]] with controlled particle size. Most contemporary vehicle-mounted systems use this approach. However, the aerosol stays airborne only for a short time. The [[brass]] particles used in some infrared [[smoke grenade]]s are typically composed of 70% [[copper]] and 30% [[zinc]]. They are shaped as irregular flakes with a diameter of about 1.7 ΞΌm and thickness of 80β320 nm.<ref>[http://orsted.nap.edu/openbook.php?record_id=9621&page=45 orsted.nap.edu] {{webarchive|url=https://web.archive.org/web/20070225010747/http://orsted.nap.edu/openbook.php?record_id=9621&page=45 |date=2007-02-25 }}</ref> Some experimental obscurants work in both infrared and [[millimeter wave]] region. They include [[carbon fiber]]s, metal coated fibers or [[glass]] particles, metal microwires, particles of iron and of suitable polymers.<ref>{{cite web|url=http://www.sew-lexicon.com/gloss_o.htm|title=sew-lexicon.com|url-status=dead|archive-url=https://web.archive.org/web/20000107061927/http://www.sew-lexicon.com/gloss_o.htm|archive-date=2000-01-07}}</ref>
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