The performance of passive devices were evaluated for the determination of nitrogen dioxide in 25 sites of San Jose and Belen, for which first, the method parameters such as limit of detection and quantification were determined and the bias and precision results were satisfactory. At least five sites in San Jose and four in Belen have values greater than 40 ug / m3, which corresponds to that recommended by the World Health Organization criteria for this contaminant. The highest concentrations are presented for commercial sites with high traffic flow where exceedances can reach up to 45%. If these values are compared with those obtained for previous years a growth rate of 11 and 13% for commercial and industrial sites recorded respectively.