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1. Ethylene Oxide Spot-On  Chemical Filter ChemDAQ has solved th e long standing p roblem in th e steri lization world of cross sensitivity in ethylene oxide gas monitors . Ethylene oxide (ETO) efficiently kills bacteria and viruses but this same bio cidal efficiency tr an slates to great to xicity in h u man s, resulting in an OSHA permissible exposure limit (PEL) of only 1 ppm over 8 Hr. TWA. To safeguard workers who use ETO, continuous monitors have been developed and ar e sold by compan ies su ch as ChemDAQ, Inc. Th e great sen sitivity needed to d etect ETO below the PEL requires the u se of electrochemical gas sensors, which can also respond to alco ho ls such as ethanol an d iso p ropanol, two compounds which find ubiquitous use in health care facilities. In add ition, trace levels of carbon monoxide (C O), well belo w its toxicity threshold can also lead to false alarms. Until recently, users had to live with the false alarms generated by alcohols or CO th at could not be remediated by changing wo rk p ractices. While reducing exposure of ETO monitors to alcohols should still be minimized thr ou gh careful work pr actice, the cr oss sensitivity p roblem has b een g reatly improved. -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0 100020003000 40005000 6000 Time Sensor Respons e Carbon Monoxide Ethanol Ethylene Oxide No Filter Filter Control sensor (no filter) Sensor w/filter Sensor w / filter Figure 1: Cross sensitivity testing of a filter with carbon monoxide, ethanol and ethylene oxide, each 10 ppm in nitrogen. Chem ical filters are normally made to remove a more reactive chemical from the air and allow less active ones to pass through. The challenge here is that ETO is a highly reactive chemic al and ethanol though it is flammable, is much less active. ChemDAQ’s patented technology (U S 7,491,547 B1) consists of a chemical fi lter that is incorporated into the sensor. The breakthrough was the development of a chemical filter that will remove the ethanol by selective oxidation but still let ETO pass through. ChemDAQ’s chemi cal filter is placed in front of the sensor and since only the ETO passes through and the alcohols and CO are removed by the filter, the sensor only ‘sees’ the ETO. The results shown above were obtained by an independent tes ting laboratory who evaluated chem ical filters. Figure 1 shows the response of three sensors, two with a filter and the other, a control, with out a filter. The sensors were exposed sequentially to carbon monoxide (50 ppm CO), ethanol (10 ppm ethanol) and ethylene oxide (10 ppm ETO) with inert gas (nitrogen) applied between exposures. As Fi gure 1 shows, the control sensor (no filter) responded to all of the test gases, but the filtered sensors only saw ETO (car bon monoxide and ethanol were effectivel y removed). All sensors gave almost identical responses to the ETO showing that the filters had litt le effect on the ETO response. This filter design has been extensively te sted to ensure their reliability under conditions that monitors are likely to be exposed to. The filters were tested from -20 to + 50 o C (the temperature limits of the sens ors) and at high and low humidity. The filters passed with flying colors and the filter capacity was determined to ensure optimum performance. We at ChemDAQ believe that use of this filter technology w ill clearly differentiate those health care facilities with interference problems from those that do not. Doc. No. SL110-A-0.00, © ChemDAQ Inc 2006, revised 2009


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