A field air-conditioner, comprising: - an air-conditioner body comprising an external casing; - an internal return duct extended inside said casing and having an inlet for the return air and an outlet for the return air, said inlet for the return air being adapted to be put in fluid communication with an environment to be air-conditioned to allow said return air, taken from the environment to be air-conditioned, to enter the internal return duct, said outlet for the return air being provided to discharge the return air in an environment which is external with respect to the environment to be air-conditioned; - an internal delivery duct, independent of the internal return duct, which extends inside said casing and comprises an inlet for the external air and a outlet for the external air, said inlet for the external air being adapted to allow the external air, taken from said external environment, to enter the internal delivery duct, said outlet for the external air being adapted to be put in fluid communication with the environment to be air-conditioned at the same time as the inlet for the return air, to introduce the external air into the environment to be air-conditioned; - a return fan arranged in the internal return duct to take the return air from the environment to be air-conditioned; - a delivery fan arranged in the internal delivery duct to introduce the external air into the environment to be air-conditioned; wherein said return fan and said delivery fan are controllable so as to be capable of regulating the flow of the return air through the internal return duct and the flow of the external air through the internal delivery duct, respectively, to selectively establish a predetermined positive or negative pressure differential between said environment to be air-conditioned and said external environment; wherein the field air-conditioner comprises an electronic control unit and at least one pressure sensor; characterized in that the at least one pressure sensor is adapted to be arranged to detect a pressure differential between the environment to be air-conditioned and the external environment, wherein said at least one pressure sensor is operatively connected to the electronic control unit to allow the electronic control unit to receive or estimate a measurement of the pressure differential detected by the at least one pressure sensor, wherein the electronic control unit is further operatively connected to the return and delivery fans (13, 23) to control such fans (13, 23) so as to automatically regulate the flow of the return air and of the external air through the return and delivery ducts (10, 20) by means of a feedback control based on said measurement or estimate of the pressure differential detected by the at least one pressure sensor. - an air-conditioner body comprising an external casing; - an internal return duct extended inside said casing and having an inlet for the return air and an outlet for the return air, said inlet for the return air being adapted to be put in fluid communication with an environment to be air-conditioned to allow said return air, taken from the environment to be air-conditioned, to enter the internal return duct, said outlet for the return air being provided to discharge the return air in an environment which is external with respect to the environment to be air-conditioned; - an internal delivery duct, independent of the internal return duct, which extends inside said casing and comprises an inlet for the external air and a outlet for the external air, said inlet for the external air being adapted to allow the external air, taken from said external environment, to enter the internal delivery duct, said outlet for the external air being adapted to be put in fluid communication with the environment to be air-conditioned at the same time as the inlet for the return air, to introduce the external air into the environment to be air-conditioned; - a return fan arranged in the internal return duct to take the return air from the environment to be air-conditioned; - a delivery fan arranged in the internal delivery duct to introduce the external air into the environment to be air-conditioned; wherein said return fan and said delivery fan are controllable so as to be capable of regulating the flow of the return air through the internal return duct and the flow of the external air through the internal delivery duct, respectively, to selectively establish a predetermined positive or negative pressure differential between said environment to be air-conditioned and said external environment; wherein the field air-conditioner comprises an electronic control unit and at least one pressure sensor; characterized in that the at least one pressure sensor is adapted to be arranged to detect a pressure differential between the environment to be air-conditioned and the external environment, wherein said at least one pressure sensor is operatively connected to the electronic control unit to allow the electronic control unit to receive or estimate a measurement of the pressure differential detected by the at least one pressure sensor, wherein the electronic control unit is further operatively connected to the return and delivery fans (13, 23) to control such fans (13, 23) so as to automatically regulate the flow of the return air and of the external air through the return and delivery ducts (10, 20) by means of a feedback control based on said measurement or estimate of the pressure differential detected by the at least one pressure sensor.