A system can include a filter assembly with a filter and a substance in the filter assembly, and at least one optical computing device having an integrated computational element which receives electromagnetic radiation from the substance. A method can include receiving electromagnetic radiation from a substance in a filter assembly, the electromagnetic radiation from the substance being received by at least one optical computing device having an integrated computational element, and the receiving being performed while a filter is positioned in the filter assembly. A detector may receive electromagnetic radiation from the integrated computational element and produce an output correlated to a characteristic of the substance. A mitigation technique may be selected, based on the detector output.