Pollution and consistent exposure to nitrogen dioxide are known as factors in respiratory illnesses, such as pneumonia and emphysema.. Therefore, careful air monitoring of public areas is necessary. A convenient and cost-effective method uses passive diffusion tubes. These tubes, treated with Triethanolamine or TEA - a nitrogen dioxide absorbent, were placed in a non-smoking environment, The Meadows School in Las Vegas, for a control and smoking environments, which consisted of several small, neighborhood casino bars also in the Las Vegas area. After the tubes absorbed nitrogen dioxide from the designated environment for a week's time, they were analyzed and then tested spectrophotometrically. The results indicated that the non-smoking environments had a nitrogen dioxide concentration of approximately 0.004–0.011 ppm, semi-smoking areas (the dining area of the pubs) had a nitrogen dioxide concentration of 0.012–0.029 ppm and the most smoky areas (the bar area of the pubs) had a nitrogen dioxide concentration of 0.023–0.048 ppm. This assay suggests that the amount of nitrogen dioxide present is directly correlated with the concentration of cigarette smoke in a given area.