From November 1995 to January 1996 El Puente staff, with CIET’s assistance, used personal monitoring equipment to measure respirable dust concentrations inside and outside its building at the foot of the Williamsburg Bridge connecting North Brooklyn and Manhattan. Six 24-hour samples collected outdoors and nine indoor samples showed higher concentrations in the outdoor samples but generally within the then U.S. ambient air quality standard of 150 µg/m³ per day for PM10 particulates. However, all but one of the samples (an indoor sample) exceeded the then proposed — and subsequently adopted — standard of 50 µg/m³ for PM2.5 (which respirable dust more closely approximates). El Puente students themselves did the electronic weighing of the samples at a university laboratory and calculated the results.