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Controlling Ventilation Air Flows

Animation Series 1:
Controlling Ventilation Air Flows
  1. Desired Ventilation Flows
  2. Overcrowded Offices
  3. Air Handling Unit Contaminated
  4. Outdoor Air Damper Opening Reduced
  5. Exhaust Not Operating Properly
  6. Supply Air to Office Shut Off or Pinched Down
  7. Economizer Operating
  8. Contaminated Outdoor Air

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Outdoor Air Damper Opening Reduced

5. Because outdoor air flow is reduced, the building is no longer slightly 4. The reduction in outdoor air had multiple effects 3. Since the pressure differential between the offices and the laboratory 2. Because total air flow out of the building can not exceed air flowing 1. The outdoor air flow was reduced, ostensibly to save energy

Mouse over the animated picture above to see messages which are referenced in more detail below.
Pressure relationships between rooms is designated at the bottom of each room (with a plus for positive and minus for negative pressure).

  1. [OUTDOOR AIR]  The outdoor air flow was reduced, ostensibly to save energy. As a result, pollutants have built up in the offices. Do you think that this is the only effect?  What do you think has happened to the exhaust system?

  2. [EXHAUST]  Because total air flow out of the building can not exceed air flowing into the building, the air that the exhaust fans are now capable of drawing out of the laboratory is also reduced because the outdoor air dampers are closed.  What will happen to the laboratory chemicals?
     
  3. [PRESSURE]  Since the pressure differential between the offices and the laboratory are reduced, laboratory chemicals may now migrate throughout the building.
     
  4. [OCCUPIED SPACES]  The reduction in outdoor air had multiple effects: It reduced the dilution of contaminants in the offices; reduced exhaust and thereby increased pollution in areas of high pollution loads such as laboratories, toilets, and copy rooms; and reduced pressure differentials between the offices and laboratory, thereby allowing laboratory pollutants to migrate into the office areas.   Reducing outdoor air BELOW APPLICABLE STANDARDS is a BAD IDEA.
     
  5. [INFILTRATION]  Because outdoor air flow is reduced, the building is no longer slightly pressurized as intended, and is now depressurized. This causes air to infiltrate from the outside into the office area.

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