Principle of Knapen system : A difference of 16 °C to 24 °C is required to displace the vitiation air from a building by means of a vertical air shaft. The Knapen Tube : The method of fixing the Knapen tube in the wall. it is a simple porous tube which is fixed with its mouth inclined outwards. As the tubes are porous the moisture of penetrates inside them. Due to difference of temperature the dry air enters in the tube from its top portion as indicated by arrow. This dry air evaporates the moisture and saturated air comes out from the lower portion of the tube. This circulation of air is due to perfectly natural laws, and remains continuous till there is any moisture left in the wall.
भारत का इतिहास और संस्कृति गतिशील है यह सिंधु नदी के किनारे और भारत के दक्षिणी भूमि में कृषक समुदायों के साथ एक रहस्यमय संस्कृति से शुरू होता है। ... चौथी सहस्राब्दी ईसा पूर्व के अंत तक, भारत अत्यधिक विकसित सभ्यता के क्षेत्र के रूप में उभरा था।