Application of metalworking fluids (MWF) in metalworking processes generates MWF aerosol/mist. Chronic exposure to this aerosol can cause serious health problems to workers such as asthma, lipoid pneumonia, dermatitis, cancer. In this paper behavior of MWF aerosol was investigated. The investigation was done in the pipe, which simulates ventilation system. The aerosol generated from 6 % O/W emulsion was investigated, as well as aerosol generated from water. SHP and water aerosol were generated by laboratory aerosol generator. Behavior of aerosol under four different air velocities was investigated. The aerosol properties were measured by optical particle size analyzer. The obtained results should be of great help for designing filters for mist separation in order to protect workers and the environment.