In the present work three different applications of DSMC method to problems of industrial interest are revised and deepen by using both other methodologies and a more updated or advanced DSMC code, compared with those already used by other researchers to solve the same problems. For each problem, a preliminary rarefaction analysis verifies that the molecular approach, therefore the use of a DSMC code, is proper. More specifically, in this work the “sophisticated” DS2V (Ver.4.5) code has been used for the simulation of the flow fields in a deposition chamber and in a micro-channel as well as for the evaluation of viscosity of mixtures. The present work is an improvement of former works about the same topics because: 1) a method is proposed for the evaluation of the film distribution on the substrate. Furthermore, as the thin film deposition process is based on expanding thermal plasma from a torch, the influences of mass flow rate and of electrical power, supplied to the gas, and of the fluid-dynamic characteristics of the plasma jet, linked to geometry of different nozzles, are analyzed. 2) Some fluid-dynamic parameters in a micro-channel, such as load loss and impulse have been evaluated. 3) Computation of the exponent of the temperature viscosity law of a mixture of gases is proposed.