68 A SHRAE Jou rna l ash rae.o rg A p r i l 2 0 0 9 Air Purification to Reduce OA

Buildings require ventilation with outdoor air to main-tain a level of indoor air quality that provides a healthy environment for the occupants of the building interior space. In simple terms, carbon dioxide and bioeffluents are generated by building occupants while various gases and par-ticulate matter (PM), some potentially harmful, are emitted by building materials and furnishings, equipment, and cleaning supplies, etc. By exhausting indoor air at an appropriate flow rate and replacing it with clean outdoor air, the concentrations of these occupant- and building material-generated gases can be maintained below objectionable or harmful levels. ASHRAE Standard 62.1-2007 prescribes outdoor ventila-tion makeup airflow rates and methods to maintain acceptable indoor air quality in commercial and institutional buildings.1 Underscoring the importance of maintaining a healthy indoor environment, Standard 62.1 has been adopted by most state and local building codes