Air Distribution
The transportation of a specified air volume to and from the conditioned space or spaces generally by means of ducts.
Air Diffusion
Distribution of the air in a space, called the conditioned space, by means of devices, called AIR TERMINAL DEVICES, in a manner so as to meet certain specified conditions, such as air change rate, pressure, cleanliness, temperatures. humidity, air velocity and noise level.
Supply
The air flow entering the conditioned spaces.
Return (recirculation)
The air volume leaving the conditioned space and returned to air treatment system.
Exhaust
Exhaust may be implemented by one or more of the following methods:
a. Extraction: exhaust in such a manner that the air is discharged into the atmosphere.
b. Relief: exhaust in such a manner that the air is allowed to escape from the conditioned space if the pressure in that space rises above a specified level.
c. Transfer: exhaust in which air passes from conditioned space to another conditioned space.
Volume Control Dampers
Components installed into air ducts or used in conjunction with air terminal devices which permit modification of the air resistance of the system and consequently a change in the air flow rate, and control of air volume in addition ,complete shut-off of the air flow
Type of dampers:
Multi leaf dampers, comprising a number of blades or shutters of parallel or opposed leaf type.
Single leaf dampers, commonly called splitter damper, the flap being mounted at one end .
Hit-and-miss dampers, having two or more splotted slides.
Butterfly dampers, with two flaps in "V" arrangement.
Fire dampers
Components which are inserted in an air distribution system between two fire separating compartments, and are designed to prevent propagation of fire. They are kept open by a mechanical restraint, whose effect is nullified under specific conditions. The damp is then closed automaticallly.
Sound attenuators (silencers)
Components which are installed in to the air distribution system and designed to reduce airborne noise which is propagated along the ducts.
Air terminal devices
A device located in an opening provided at the boundaries of the conditioned space to ensure a predetermined motion of air in this space.
Supply Air terminal devices
An air terminal device through which air enters in to a conditioned space . It usually consists of one or several deflecting members which ensure reduction of air velocity in the zone between the air terminal device and the conditioned zone as well as efficient mixing of the supply air with the air in the conditioned space.
Moreover supply air terminal device also determine the direction of air jet(s)