An auxiliary device (1) suitable to allow exhalate collection on an adsorbent cartridge, comprising:- a cylindrical sampling chamber (101), having an outlet port (21) in communication with an environment accommodating the cartridge- a cylindrical inhalation chamber (102), having a port (22) for communication with the outside, to allow inletting of outside air into the inhalation chamber (102)- a first passive-type check valve (31), interposed between the sampling (101) and inhalation (102) chambers to selectively set them in communication and- a second passive-type check valve (32), arranged at said port (22) for communication with the outside to selectively allow an inletting of outside air into the inhalation chamberwhich device (1) further has an inlet port (20) in communication with a patients mouth for receiving a flow of exhalate,wherein the overall configuration is such that, during an expiratory act causing a flow of exhalate being inlet from said inlet port (20), the first valve (31) sets in communication the inhalation chamber (102) with the sampling chamber (101) and the second valve (32) interdicts the inletting of outside air into the inhalation chamber (102), and vice versa at an inspiratory act (Figure 1A).
