Gas detection methods have been changing and evolving and awareness has heightened as well, along with the ever changing methods of sterilization. To answer your question regarding what “most” hospitals are using to monitor EtO, a fair response would be narrowed down to either electrochemical sensors or gas chromatographs (GCs). Interscan has sold close to 1000 EtO monitors. Of this 1000 nearly 50 have been sold to V.A. Hospitals. We are not aware of the existence of many (if any) photo-acoustical instruments in the field. IR doesn’t seem to be very common either, but there are no doubt, some in use.
Solid State sensors were certainly more predominant in the early 80’s when the TLV for EtO was 50 ppm, and when the 88/12 mixture (Freon/EtO) was in use. In this case, specificity to EtO was not considered (as the solid state sensor was actually responding more to freon than EtO.) Also at that time, instruments did not necessarily exist which could measure low enough levels of EtO to address long term exposure to low ppm levels.
GCs were introduced on the scene primarily by sterilizer manufacturers who (in an attempt to increase marketability) included an EtO monitor as part of their entire sterilizer package. Ironically they originally used the solid state sensor companies as this method was far less expensive. This quickly became troublesome since the solid state sensor is specifically designed to be nonspecific. After determining they were spending too much time addressing the EtO monitoring problem, they incorporated GCs (At that time manufactured by Baseline) into their overall product offering.
A GC – primarily to be used as a laboratory analytical device (as opposed to a field monitor) provides specificity by running the gas sample through chromatographic columns. The actual detection device within the GC, a Photo Ionization Detector (PID) is by nature and design NON-specific. Outwardly the GC appears to be 100% specific to EtO, and in fact IS until the chromatographic columns deteriorate and degenerate due to exposure to IPA and other solvents.
Since it is not primarily the responsibility of SPD managers to be instrumentation experts along with all their other duties and responsibilities, it is understandable for them to believe that GCs are problem free and the answer to false alarm scenarios.
Not discussed herein is the use of badges which are still rather prevalent in hospitals. They are however becoming less popular since they do not offer real time and true exposure documentation regarding long term low level exposure.