Based on the analysis results,a flow chart of fog-monitoring using the multi-spectral synthesis method is given and the fogs which occurred at 13:30 on December 13,2004 in North China Plain as well as at 14:15 on December 14,2004 in Sichuan Basin are detected.

A comparison between Mark 4 and Mark 5 oil mist detector produced by the Graviner Ltd is made and an analysis of the feature of Mark 5 oil mist detector is given,and then,an opinion about the microcomputer utility in some measure and control equipment of engine room is presented.