Sub-part-per-million diffusional sampling for ethylene oxide with the 3M #3550 ethylene oxide monitor

A method is described for the collection and determination of ethylene oxide in air below the 1 ppm level. A passive diffusion-type monitor adsorbs the contaminant on a treated charcoal disc and converts it to 2-bromoethanol. This compound is then desorbed, injected into a gas chromatograph, and evaluated by electron capture detection. Laboratory testing was done by simultaneously challenging the monitors and Qazi-Ketcham charcoal tubes with 0.20 to 0.80 ppm ethylene oxide in air. At these levels, the bias of the monitors was +0.48% with overall accuracy of 13.8%; for the Qazi-Ketcham tubes it was -11.2% with an overall accuracy of 22.7%, well within the +/- 25% OSHA requirement. Field validation tests were performed using a specially-constructed chamber which simultaneously draws the work environment air over the monitors and through charcoal tubes to assure uniform sampling. The tube samples were analyzed in two laboratories. Results from the two collection devices agreed within 7.4% in the same laboratory, and results of the Qazi-Ketcham method between laboratories agreed within 21%. All results, lowest to highest, were within the OSHA +/- 25% limit.