Plenum ceiling

Fig. 11 Self-contained terminal HEPA filtration modules installed in a T-bar suspended plenum ceiling in a laminar-flow application. (Courtesy of American Air Filter, Inc., Louisville, Kentucky.)...

Lift a ceiling tile and examine the plenum for potential problems. Walls or full-height partitions that extend to the floor above can obstruct or divert air movement in ceiling plenums unless transfer grilles have been provided. If fire dampers have been installed to allow air circulation through walls or partitions, confirm that the dampers are open. Construction debris and damaged or loose material in the plenum area may become covered with dust and can release particles and fibers. 

Full use IS made of ceiling diffusers, which ensure that the cold air spreads out over a wide area before dropping. Perforated ceilings may be used, with the ceiling void being the plenum chamber. A typical downward system is shown in Fig. 9.28. 

The building was strengthened by a bottom to top shear wall within the building and it has been left exposed. A commercial ground floor was also established. There was a mechanical room on the top floor. This has now been converted into a gym and immediately below are the executive offices. The original floor to ceiling height was 14-16 feet and a raised floor (18") was introduced. It has wood core, metal-faced panels with a pressurized plenum... 

It is worth stressing that the calculations done in this work have ignored HC1 decay. This is very important since the rate of HC1 decay in sorptive surfaces (such as concrete or ceiling tile) is extremely high (half lives of HC1 of less than 1 min have been calculated for a plenum with such surfaces [32]). 

Notes 1) The structure, consisting of the plenum chamber filter, shall be of such design that it can be supported by means of four (4) steel columns, one (1) at each corner. 2) Plenun chamber shall be of sufficient strength bracing to prevent wall, floor or ceiling from pulsating or oscillating. 3) For ammonia/urea plants or other installations with ammonia in the atmosphere, no copper, alianinum or their alloys shall be used for parts exposed to the air. 4) Seals filter material shall be resistant to vapors present in the inlet air (ammonia, hydrocarbons, etc.). 5) Unit shall be completely assembled and shipped as one unit. 6) Instruments controls to be conpletely piped and wired. 7) Outlet connection screen (0.25 in.) (6 mm) wire mesh, with back up bars to withstand seven (7) psi/0.5 kg/cm Press, across the screen. 

A return air opening either completely ducted from the occupied zones or through a short length of duct from the ceiling plenum that dumps all the return air into the AHU room. This would typically constitute 90% of the total supply air flow. 

Each floor of the building was divided into 2 air-conditioned zones, which were served by their respective AH Us, located at each end of the floor. Linear diffusers were employed for supply air and the return air system was based on the ceiling plenum concept. The floor plans for the 4th, 11th and 17th floors, in which the studies were carried out, are quite similar and a schematic representation is provided in Figure 10.7. 

Filter Location HEPA filters may be installed in a facility either within an air handler or at the inlet to a plenum above the clean room or in the clean room ceiling. High-velocity HEPA filters, that is, filters with a face velocity up to 500ft/min, are frequently installed in air handlers serving Class 100,000 clean rooms and are also used in make-up air handlers. Where hazardous materials may be trapped by the filters a bag-in-bag-out filter arrangement, such as that depicted in Figure 16, may... 

To provide HEPA filtered air over a limited area within a larger controlled space, a ceiling-mounted pressure plenum may be used. This plenum has an air distribution means at its lower face that permits air to be introduced in a unidirectional manner over the critical process area. Refer to Figure 18. 

HEPA hlters are installed at the upper face of the pressure plenum and the plenum is pressurized with hltered air. The ceiling-mounted HEPA hlters have a face velocity up to 100-120ft/min. This is somewhat higher than the HEPA hlters serving the rest of the clean room. The hlters are commonly supplied with air by a... 

Plenum - The space between a hanging ceiling and the floor above or roof usually contains HVAC ducts, electrical wiring, fire suppression system piping, etc. 

Industrial rules of thumb generally equate the ceiling-space height to the plenum-space width and to the combined sticker-spacing height. Hydraulic tests on a model kiln confirm the former rule (Nijdam and Keey, 1999), and the latter is verified by a pressure-drop analysis (Nijdam, 1998). 

Patel J A. (1982) The Distribution and Regulation in Nerve Ceils and Astrocytes of Certain Enzymes Associated with the Metabolic Compartmentation of Glutamate, in Neurotransmitter Interaction and Compartmentahon (Bradford A.F, ed ), pp. 411-429, Plenum, New York. 

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