Indoor Air Quality

Indoor air quality is important to the "V" in HVAC; ventilation.  Indoor air quality has always been a term that I assumed was about the basics of getting fresh air and avoiding any materials or equipment that may expel toxins into an interior setting.  While this is true, I did some research to understand IAQ on a more specific level.


According to Maryrose McGowan's Interior Graphic Standards, air quality is essential for comfort and productivity and most importantly, IAQ promotes good health.

Indoor Air Quality will be compromised if:

-inadequate ventilation doesn't provide enough outside air

-chemicals used in cleaning and office products get trapped inside a building

-outdoor pollutants enter and are trapped inside

-mold or other microorganisms grow, multiply and disperse particles through heating, air conditioning and ventilation systems 

Diagram of HEPA filter. http://en.wikipedia.org/wiki/File:HEPA_Filter_diagram_en.svg

In order to filter out gases and particles we need to use:

-lower efficiency filters

-high-efficiency particulate-arresting (HEPA) filtration

-absorption with activated carbon

Filters are placed in the ducts at various points to stop particles from passing through.  There are two

types of commonly used filters:

-woven fiberglass filters which have a lower density weave, air flows more freely through them so smaller fans are needed and less energy is needed, however they only trap larger particles and fewer of them.

-HEPA filters which catch 99.97% of all particles, made from a single sheet of water repellent fiber that is pleated to provide more surface area, because they are more densely woven, they require larger and more energy intensive fans, making their cost greater expense economically undesirable in buildings, also noisier because of larger motors, they are usually used in spaces that are especially sensitive to contamination. For example; an operating room.

The decision between the types of filters depends on the project's budget and the typology of the project.  Indoor air quality is something we can not see, therefore may sometimes be forgotten about, but is a major consideration for interior designers.    

Natasha Bargen

Mechanical Engineer

source: Maryrose McGowan's Interior Graphic Standards, page 99.