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Pressure Relationships

Animation Series 2:
Pressure Relationships
  1. Balanced Flows are Precarious
  2. Unbalanced Flows Pollutes Office

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Unbalanced Flows Pollutes Office

4. The flow of outdoor air into the building automatically increases... 3. Copy room exhaust and supply are operating normally... 2. Since the kitchen exhaust fans are running full... 1. It's lunch time. When preparing lunch, the main exhaust fans...

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. [KITCHEN EXHAUST]  It’s lunch time. When preparing lunch, the main exhaust fans in the kitchen are turned on. These are drawing a large volume of air out the exhaust so that the kitchen and cafeteria area under greater negative pressure that draws more transfer air from the office area.  What happens in the office area?.
     
  2. [OFFICE AREA]  Since the kitchen exhaust fans are running full, the kitchen is drawing enough transfer air from the office area to place the office under negative pressure relative to the copy room. This draws copy room exhaust into the office environment. Complaints occur only around lunch and only if the copy room is being heavily used.  By the time the building engineer arrives to investigate in the late afternoon, the kitchen exhaust fans are turned down, and the problem has gone away. Other offices in the building think that the IAQ was actually better than other times of the day.   The problem recurs only periodically. The engineer thinks these particular occupants are just periodic complainers.   Sound familiar?
     
  3. [COPY ROOM]  Copy room exhaust and supply are operating normally.  But since the kitchen exhaust fans are running at full load, the draw from the kitchen is sufficient to draw copy room contaminants into the office area and generate complaints.
     
  4. [OUTDOOR AIR]  The flow of outdoor air into the building automatically increases when the kitchen exhaust fans are turned on full. The extra outdoor air replaces the air removed by the added exhaust from the kitchen area.  However, although the building itself has added dilution ventilation, giving rise to improved IAQ elsewhere in the building, air the office next to the copy room becomes more polluted when the copy machines are heavily used during the lunch period.

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