ASHRAE Indoor Air Quality – IAQ Procedure

Determine minimum OA rate for each zone using IAQP by following steps:

  1. Identify all contaminants-of-concern and mixtures-of-concern for the zone.* For simplicity we’ll refer to all of these as “pollutants.”
  2. Identify both indoor and outdoor sources for each pollutant.
  3. Determine the emission rate for each pollutant from each identified source.
  4. Specify a concentration limit for each pollutant.
  5. Design limit for perceived IAQ: minimum percentage of occupants or visitors satisfied with air quality in completed building.
  6. Calculate minimum breathing zone OA rate for pollutants using mass balance calculations to meet concentration limits.
  7. Find the OA rate required to meet the perceived IAQ limit by conducting a subjective evaluation in the completed building or by establishing that the current zone design meets the criteria for a “substantially similar zone” wherein a successful subjective evaluation has been conducted.
  8. For each zone, find the minimum breathing zone OA rate—the largest OA rate among those determined by mass balance for each pollutant or the OA rate determined by subjective evaluation—whichever is greater.
  9. Finally, find system-level OA intake flow based on the breathing zone OA rate found for each zone.

Standard 62.1 allows designers to apply the IAQP in some zones within a system, and the VRP in other zones, and it requires designers to document design assumptions and calculations, but here we focus on the nine steps listed.

*Example impact-mixture categories based on Office of Environmental Health Hazard Assessment (OEHHA) table:

Pollutant category Type Examples Example sources Impact
particulate matter solid dust (less than 100 µm) wind, volcanoes, grinding, demolition, burning, fuels unpaved roads and so on asthma, nose and throat irritation, lung damage
bioaerosols living things, including viruses, bacteria, fungi, mites, plants and insects allergies, asthma, various diseases, including tuberculosis, Legionnaire’s disease, and influenza
liquid mist cooling towers evaporation may increase concentration of bioaerosols
fog condensation evaporation may increase concentration of bioaerosols and very small particles
gaseous contaminants inorganic ammonia cleaning products respiratory irritant
ozone electrostatic appliances, printers, copiers, outdoor air reduced lung function, asthma, eye irritation
carbon monoxide incomplete combustion, outdoor air respiratory system damage
radon soil lung cancer
organic formaldehyde building materials, adhesives, insulation eye, nose, and throat irritation, asthma, respiratory symptoms
benzene burning, automobile exhaust, some glues, paints, and detergents cancer
other volatile organic compounds (VOC) people, processes, cleaning products odor, wide range of physical symptoms
mixtures source mixtures smoke burning organic material see particulate matter
tobacco smoke burning tobacco cancer; see particulate matter
diesel exhaust diesel fuel combustion cancer; see particulate matter, inorganic and organic gases
smog products of combustion see ozone and particulate matter
impact mixtures** example constituents: acetaldehyde, acrolein, ammonia, etc. multiple sources respiratory system impact
example constituents: arsenic, benzene, carbon disulfide, etc. nervous system impact
example constituents: benzene, butadiene, carbon disulfide, etc. reproductive system impact