Selectivity of ChemDAq Ethylene Oxide Monitors

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1. ChemDAQ Inc. • 300 Business Center Drive Suite 330 • Pittsburgh, PA • 15275 phone 412.787.0202 • fax 412.788.2526 ©ChemDAQ Inc, 2008. Doc. No. CL- 100 -A-0.00 Selectivity of ChemDAQ Ethylene Oxide Monitors Introduction Ethylen e oxid e (ETO) is a commonly used sterilan t g as, used to sterilize med ical supplies and equipment that canno t b e hea t or steam sterilized. Ethylen e oxid e has very high efficiency, bu t is also tox ic and h as been classified by th e Internation al Agency for Research on Cancer as a class I known human carcinogen. In ligh t of EtO’s potential health hazards, the Occupation Safety and Health Administration (OSHA) has promulgated regulations under 29 CFR 1910.1047 th at s et th e permissib le exposur e limi t (PEL) for E tO to 1 ppm, calculated as an eigh t hour time weighted average, and to 5 ppm excursion lim it, calculated as a 15 minute tim e weighted average. OSHA also requir es promp t aler t in th e even t a major leak (1047(h)(2) and th at exposur e records be kept for 30 years. The ChemDAQ sterilant gas detection system has been designed to meet all of the OSHA requirements for EtO providing both 15 minute and 8 hours time weighted average readings as well as continuous real time gas readings. Interference Problems Th e ChemD AQ monitor, (and g as monitors from other manufacturers) uses electrochem ical sensors that respond w ell to E tO with adequ ate sensitivity to EtO, however thes e sensors also respond to other easily compounds th at ar e found in th e healthcar e workplace. Examp les of such compounds ar e ethano l and isopropanol vapors and low levels of carbon monoxid e (<< OSHA PEL of 50 ppm). Since the monitor is unable to distinguish between a sensor response to an alcohol and EtO and the resulting false alarms have plagued electrochemical based monitors for EtO from all suppliers. This interference problem has given electrochemical sensors for EtO a poor reputation in the healthcare industry, because of the wi despread use of alcohol based cleaning and disinfection products. ChemDAQ Solution – The Spot-On ™ Filter ChemDAQ has developed a proprietary chemical filter th at is placed in th e sensor’s g as path. This filter is currently patently pending. Th e filter rea cts chemically with both alcohols, carbon monoxid e and mos t other interference gas es bu t th e filter still lets th e E tO pass through. Thus since only th e E tO reach es th e sensor, the monitor is highly specif ic and false alarms rarely occur. The filter is consumed upon reaction with the interferent gas and must be replaced periodically. ChemDAQ replaces the filter each time the sensor is calibrated. ChemDAQ sensors are periodically swapped out with fresh calibrated sensors to ensure peak performance. Factory calibration avoids many of the problems associated with field calibration with reactive gases. Residual Cross Sensitivity Wh ile th e Spot-On filter does remov e mos t interference gas es, E tO is no t th e only g as th at w ill pass through filter. Testing has shown tha t alkenes such as ethylen e (CH 2 =CH 2 ) will also pass through th e filter . Other alkenes such as propylen e behav e similarly and wil l pass through th e ChemD AQ filter. In som e situations this can cause a problem. In once case, a customer, a medical equipment manufacturer, was using liquid propane forklifts (LPG) near their EtO monitors and was seeing some interference problems even with sensors with fresh filters. It turns out that LPG can contain up to 20 % propylene and trace levels of this gas ending up in the air and resulted in a reading on the nearby ChemDAQ EtO monitor. Once the problem was identified, it could be solved. However LPG and other sources of alkenes are rarely used in healthcare settings and so the cross sensitivity to alkenes is generally not an issue in this application.


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