Ecology units are ventilation equipments whose use is recommended in kitchen exhaust systems , which serve to clean greasy and dirty exhaust air . With the increase of environmental consequences in the 21st century , severe restriction have been imposed on the release of industrial wastes to the environment , and particularly on the release of flue gas and kitchen exhaust systems to the atmosphere. It is known that the volatile organic compounds ( VOC ) and other particular based substances in the kitchen exhaust systems creates a huge pollution in the air . in many countries , significant restrictions have been imposed on the release of odorous substances to the atmosphere by the regulation issued by the Ministeries of the Environment. n nWith the introduction of the new residential concept in big cities the rise in so-called “ all-in-one “ projects has led to some problems with air quality . This is because the concentrated kitchen exhausts from the large restaurants and dining areas in these projects have a negative impact on the daily functioning of people occupying the residential , office , and hotel areas that are in close proximity to these areas. n nIn the absence of measures , the accumulation in ducts exhaust equipment of substances such as grease , soot and smut that are released during cooking raises fire risk to high levels later on. In addition to fire risk , the accumulation of these substances causes the intake fans and filters to be quickly clogged , the ducts to be quickly contaminated and consequently lead to a rapid rise in expenses. n nTo meet the needs born of all such problems the German VDI 2052 and British DW/172 standards have been created , specifying some requirements for kitchen exhaust systems .