CLASSIFICATION OF HOUSE CHARACTERISTICS IN A BOSTON RESIDENTIAL NITROGEN-DIOXIDE CHARACTERIZATION STUDY

Building characteristics of dwelling units in the metropolitan Boston area were statistically sorted on the basis of observed associations b etween the variables. First, associations between categories of house characteristics were determined by cross-table analyses with a pair-wi se chi-square test. The key characteristics, which have a significant relationship with many other characteristics, were used to classify th e dwelling units into several groups. Two key characteristics, i.e. bu ilding type and size of building, were determined. Houses were divided into threee groups: single-unit building, small multi-unit (2 to 4 un its) building, and large multi-unit (5+ units) building. The building type was not associated with indoor source, but was significantly asso ciated with volume of dwelling unit, air exchange rate, and indoor and outdoor NO2 concentrations. Lower airflow, smaller volume units, and higher outdoor NO2 concentrations, in combination with other factors, result in higher indoor NO2 concentrations in multi-dwelling residenti al units (apartments and condominiums).