I understand that a lot of oil makers have removed TCP (esp the o-isomer but the others aren't v nice either) and that airlines are using them - maybe WCT could suggest what other compound they might use?? Even so, as I mentioned, there are lots of other nasties in synthetic oils and the thermal breakdown products thereof. Effective filtration would almost certainly required (see PALL website) but I don't know how CAQ monitoring would work in practice....how accurate its is for all possible contaminants, how easy/expensive it would be to fit and how prone are such systems to false alarms....anyone know more?