Extraction method for extracting the air in an injection mould, said mould comprising - closing means; - one or more injection cavities provided with at least one injection nozzle for introducing the hot material in a liquid state; - at least one ejector device formed by a housing for an ejector pin responsible for extracting the already moulded part; - an air duct connected to a vacuum pump or a suction device transversely intercepting at least one housing of an ejector pin for causing a suction of the air from inside the mould through the existing space between said ejector pin and said housing, - an additional air removal conduit which intersects with the air duct connected to the vacuum pump or the suction device, said method comprising the steps of: a) closing the mould; b) activating the air duct connected to the vacuum pump or the suction device transversely intercepting the housings of the ejector pins of the ejector devices producing the suction of the air from the mould; c) injecting the plastic into the mould; d) filling the mould; and e) cooling and ejecting the part wherein the air duct and the vacuum pump or the suction device are activated throughout the entire injection of material into the mould, characterised in that the additional air removal conduit comprises a piston responsible for activating a valve housed in the injection cavity itself and in that once the mould is closed, simultaneously with the air extraction through the ejector devices but before injecting the plastic into the mould, it additionally comprises the steps of: a1) activating the additional conduit and the valve; a2) extracting the air from inside the mould through the intersection of the air duct with the additional conduit; and a3) closing the valve. - closing means; - one or more injection cavities provided with at least one injection nozzle for introducing the hot material in a liquid state; - at least one ejector device formed by a housing for an ejector pin responsible for extracting the already moulded part; - an air duct connected to a vacuum pump or a suction device transversely intercepting at least one housing of an ejector pin for causing a suction of the air from inside the mould through the existing space between said ejector pin and said housing, - an additional air removal conduit which intersects with the air duct connected to the vacuum pump or the suction device, said method comprising the steps of: a) closing the mould; b) activating the air duct connected to the vacuum pump or the suction device transversely intercepting the housings of the ejector pins of the ejector devices producing the suction of the air from the mould; c) injecting the plastic into the mould; d) filling the mould; and e) cooling and ejecting the part wherein the air duct and the vacuum pump or the suction device are activated throughout the entire injection of material into the mould, characterised in that the additional air removal conduit comprises a piston responsible for activating a valve housed in the injection cavity itself and in that once the mould is closed, simultaneously with the air extraction through the ejector devices but before injecting the plastic into the mould, it additionally comprises the steps of: a1) activating the additional conduit and the valve; a2) extracting the air from inside the mould through the intersection of the air duct with the additional conduit; and a3) closing the valve. a) closing the mould; b) activating the air duct connected to the vacuum pump or the suction device transversely intercepting the housings of the ejector pins of the ejector devices producing the suction of the air from the mould; c) injecting the plastic into the mould; d) filling the mould; and e) cooling and ejecting the part wherein the air duct and the vacuum pump or the suction device are activated throughout the entire injection of material into the mould, characterised in that the additional air removal conduit comprises a piston responsible for activating a valve housed in the injection cavity itself and in that once the mould is closed, simultaneously with the air extraction through the ejector devices but before injecting the plastic into the mould, it additionally comprises the steps of: a1) activating the additional conduit and the valve; a2) extracting the air from inside the mould through the intersection of the air duct with the additional conduit; and a3) closing the valve. a1) activating the additional conduit and the valve; a2) extracting the air from inside the mould through the intersection of the air duct with the additional conduit; and a3) closing the valve.