Our workplace requires fixed gas detectors in a few areas, just to ensure that some of the chemicals we work with don't leak out into the atmosphere. Whilst I don't know a whole lot about how all of this works (being in the office most of the time) I do know that we only purchase detectors from Active Environmental and have been doing so for years - this clearly says a lot about the quality of the equipment and the level of service that we receive. From speaking with some of the guys who work with the detectors, they have said that they are easy to use and are known for giving accurate readings - both of these are always a good thing!