Comparative study of four different scavenging systems for nitrous oxide

A field investigation was conducted to evaluate and compare four of the commercially available scavenging systems for nitrous oxide in a dental operatory. In 1977, the National Institute for Occupational Safety and Health (NIOSH) recommended that no worker be exposed at time-weighted average concentrations greater than 50 part per million in a dental office per administration. Since that time, several companies have developed scavengers to capture waste anesthetic gas. The scavenging systems tested in this study included the "Brown," "Blue," "Porter," and the "Fraser Harlake." The anesthetic gas analyzed in all measurements was nitrous oxide. Twenty-minute personal air samples were taken from the dentist's breathing zone. Air samples were collected in a Tedlar bag (50 liters) using a personal air sampling pump operating at a flow rate of 2.0 liters per minute. The air sample was analyzed using a Wilks-Foxboro, Maran 1A Infrared Gas Analyzer. A pair of Nitrox dosimeters was taped side by side next to the open end of the Tygon tubing to test the similarity between the dosimeters and the Miran 1A results. The results of the study indicated that the six pairs of scavengers were not statistically different at an overall ? = 0.05. Power calculations indicate high probability the a Type II Error resulted, since only 13 of the 30 patients (required to achieve this ?-level) were obtained. The results suggest that, given a larger sample size and similar outcomes in the test results, there could be b difference between four of the six pairs. The results of all four scavengers exceeded the NIOSH recommendation of 50 parts per million. Comparisons between the Nitrox dosimeters and the bag samples showed no statistically significant difference (p > 1.10). Also, no statistical significance was shown in the results of the paired Nitrox dosimeters ( p> 0.10).