Evaluation of a system of passive sampling of CPVC of nitrogen dioxide in the air

Passive diffusion tubes were made to detect NO 2 concentration in the air with chlorinated polyvinyl chloride's tubes (CPVC). Evaluation was carried out by comparing the results obtained in 2008 with the Griess-Saltzman modified method, according to World Health Organization guidelines. Statistical analysis done with linear minimal squares and Wilcoxon ranges and signs found no significant difference between both methods. Relative bias in 7 samples varied from - 19.05% to 24.44% with an average value of 5.76%. Results indicated that the passive tubes overestimated the concentration of NO 2, however, this bias was not greater than the ones reported by other authors. The passive system's precision, measured by variation coefficient in a four tube sample, was in the 5.2% to 10.6% range, again, similar to other reported ranges.