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Indoor Environment Report — February 2008

A dirty ceiling is no reason to clean your HVAC system

A common misconception holds that dirty streaks on ceiling tiles around registers and diffusers means ducts need cleaning, when in fact the ductwork is not dirtying the ceiling tiles.

Dust and dirt around diffusers indicate that the air in the room is dirty. This, however, won’t tell you where the dust and dirt originates.

Air, like water, is highly mobile. Both possess the same characteristics in terms of physics and fluid dynamics. If the air in the ductwork is clean and the air in the room is dirty, When air in the ductwork exits the diffuser and enters the room, it displaces air already in the room.

Clean, ducted air coming out of the HVAC system through a vent sets the already dirty room air in motion, forcing it to impact nearby surfaces, such as walls and ceilings. The force and angle of the air coming from the duct will determine where the dirty air will go and the size of the area it affects. This same thing will occur at any point where air exits the HVAC system including, leaky duct joints and holes.

To further show the relationship between diffused air and dirty room air, take a walk through your building and inspect the HVAC vents. You will see that vents located near the greatest source of room dust are dirtier than vents served by the same HVAC system in areas where there is less dust. Photocopy rooms, loading docks, and lobbies are prime areas where the air is often dirtier, as evidenced by streaks near the diffusers.

Maintaining Good Indoor Air Quality with I-BEAM

Since, according to the U.S. Environmental Protection Agency, indoor air pollution is among the top five environmental health risks, maintaining clean indoor air is of paramount concern to building owners and managers.

A valuable tool for evaluating the quality of indoor air is the EPA’s Indoor Air Quality Building Education and Assessment Model (I-BEAM). First released in 2002, it is designed for use by building professionals and others interested in indoor air quality in commercial buildings.

I-BEAM updates and expands EPA's Building Air Quality guidance and is offered as a comprehensive state-of-the-art guidance for managing IAQ in commercial buildings. I-BEAM contains text, animation/visual, and interactive/calculation components that can be used to perform several tasks including:

  • Conducting an indoor air quality (IAQ) building audit
  • Diagnosing and resolving IAQ related health problems
  • Establishing an IAQ management and maintenance program to reduce IAQ risks
  • Planning IAQ compatible energy projects
  • Protecting occupants from exposures to construction/renovation contaminants
  • Calculating the cost, revenue, and productivity impacts of planned IAQ activities.
I-BEAM is available free on CD-ROM. To obtain a copy, click here.

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