The oily particles produced by aerosolization of the Metalworking fluids (MWFs) pose a threat to human health. To quantify the transmission of oily particles for developing mitigation strategy, the possible particle volatilization, adhesion and coagulation during air transmission should be determined. Therefore, this study firstly by measured the particle size distributions at and away from the emission source in the laboratory. Then, to further verify the results obtained in the laboratory, the particle size distributions of oily particles in a machining workshop were measured. Meanwhile, to better understand the source characteristic of oily particles, this investigation measured the water content of the oily particles in the machining workshop because such a parameter could affect the removal performance of oily particles by filtration. The results revealed that the particle size distributions of oily particles at different locations were similar regardless of the laboratory measurement or on-site measurement. Thus, the evolution of particle size distribution of oily particles during air transmission could be ignored. Besides, the oily particles in the air had a water content of 22.6 % when the MWFs with a water content of 95 % was used during turning process. Although the oily particles in the air contained a certain amount of water, they were difficult to volatilize. The oily particles in the air might mainly consist of pure oily particles and water-in-oil particles. The results in this study could provide guidance for developing better control strategies of oily particles in machining workshops.