25 October 2004
Figure 2-2. Decision tree for replacement air design.
Space Pressure Modulation. Control the ventilated space pressure by
modulating the quantity of replacement air. Use a variable frequency drive (VFD) motor
to control the fan speed (see MIL-HDBK-1003/3, Heating, Ventilating, Air Conditioning,
and Dehumidifying Systems for information of VFD motors). Using barometric dampers
to control replacement air quantity is inefficient and unreliable. Sensor controlled
transfer grilles are acceptable provided there will not be a problem with contaminated