DPM is a gas treatment equipment used to purify the NITROGEN from oxygen and humidity residuals. Normally it is used for nitrogen produced by on site-generators, but sometimes it could be used to obtain ultra-pure and iper-dried gas from bottled nitrogen. Working principle is to use a DEOXY tower, containing a catalyst, to burn the residual oxygen contained in nitrogen; to obtain this purpose, an hydrogen flow is mixed, inside the deoxy, together the nitrogen to be purified; of course the whole process is controlled by an electronic system (MassFlow-PLC) that defines the exact quantities of N2 and H2 to be mixed. The following step is to dry the purified gas, and this is obtained through chiller driers and alumina towers, allowing to reach a dew point up to -80°C. The most important advantage of this system, is that the customer can use a small nitrogen generator, to obtain large quantities of low-purity nitrogen, which can be,later, purified, saving a lot of electric energy for the required compressed air. Infact the quantity of nitrogen produced by an on site generator is inversely proportional to its purity.