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Figure 1: Components of a centrifugal fan An external motor belt driven inline centrifugal fan discharging inline to the exterior of a building through a duct. Unlike non-inline/non-concentric impeller casing design with a cutoff blade above, the concentrically symetric cylinder casing and impeller geometry of inline type redirects the outflow around so that it is parallel to the inflow of gases.
The ductwork airtightness level is the airflow rate through ductwork leakages divided by the ductwork area. It is recommended to test at least 10% and 10 m 2 of the duct surface including all duct types and a variety of sizes and components. The ductwork surface area is estimated according to EN 14239. [11]
Supply diffusers in the ceiling are fed by fan coil units in the ceiling void or by air handling units in a remote plant room. The fan coil or handling unit takes in return air from the ceiling void and mix this with fresh air and cool, or heat it, as required to achieve the room design conditions. This arrangement is known as 'conventional ...
The most common UFAD configuration consists of a central air handling unit delivering air through a pressurized plenum and into the space through floor diffusers. Other approaches may incorporate fan powered terminal units at the outlets, underfloor ducts, desktop vents or connections to Personal Environmental Control Systems. [8]
Pressurisation ductwork (sheet metal) externally fireproofed with pressed vermiculite boards, stapled together. Pressurisation ductwork made of Durasteel. Pressurisation ductwork is a passive fire protection system. It is used to supply fresh air to any area of refuge, designated emergency evacuation or egress route.
Smoke damper may be used to prevent the spread of smoke from the space of fire origin to other spaces in the same building. A combination of fans and dampers can exhaust smoke from an area while pressurizing the smoke-free areas around the affected area (inhibiting smoke infiltration into additional areas).
Air streams are mixed to save energy and improve energy efficiency by partially recirculating conditioned air.. The most common application for an air-mixing plenum is the mixing of return air (or extract air) with fresh air to provide a supply air mixture for onward distribution to the building or area which the ventilation system is serving. [1]