An automatic ceiling diffuser system for a room, said system being suitable for the heating, cooling and the ventilation of said room by radiation and thermal convection, said system comprising at least one modular unit intended to be hung on the ceiling of the room, said modular unit comprising: a peripheral frame with at least one line of attachment of a diffusion element such as a stretched fabric located in the lower part thereof opposite the ceiling; on one or a plurality of the faces thereof, said peripheral frame comprising a slot for blowing air toward the room, a diffusion element such as a stretched fabric, hung on the hook line of the peripheral frame, visible from the room and forming the horizontal lower face of the modular unit; an upper cover forming the upper side of the modular unit facing the ceiling; a tap-off branch for blowing air, attached to the suction box of the modular unit and permitting the injection of treated air into the interior volume of the modular unit; characterized in that same comprises a channel of articulated deflectors (10, 11) formed by an upper articulated deflector and a lower articulated deflector, attached to the peripheral frame at the level of the air blowing slot and allowing the blown air to be directed at a defined angle with respect to the ceiling varying from 0°, namely parallel to the ceiling when cold air is blown into the unit, to a maximum of 70° when hot air is blown into the modular unit; an thermostatic actuating means for actuating said channel of articulated deflectors via a means of actuating the deflectors (10, 11) such as an actuating rod and imparting to the channel a blowing angle dependent on the temperature of the treated air injected into the modular unit, said thermostatic actuating means comprising a piston the output stroke of which depends on the air temperature wherein said thermostatic actuating means is immersed, a return spring for exerting a force opposed to the stroke of the piston of said thermostatic actuating means and thus returning it to its minimum stroke when cold air is blown into the modular unit, and where said channel of articulated deflectors (10, 11) includes an articulated means for maintaining parallelism positioned in said channel and connecting the upper and lower articulated deflectors (11 and 10) to the articulation points B and C respectively, said upper and lower articulated deflectors (11 and 10) attached to the peripheral frame at the articulation points A and D defining together with the articulation points B and C of said articulated means for maintaining parallelism, a parallelogram A-B-C-D imposing a parallelism of the opposite sides thereof, and where said modular unit further comprises a connecting tap-off for air intake attached to the upper cover of the modular unit and communicating with a suction box provided with a filter sucking up ambient air from the upper cover of said modular unit. a peripheral frame with at least one line of attachment of a diffusion element such as a stretched fabric located in the lower part thereof opposite the ceiling; on one or a plurality of the faces thereof, said peripheral frame comprising a slot for blowing air toward the room, a diffusion element such as a stretched fabric, hung on the hook line of the peripheral frame, visible from the room and forming the horizontal lower face of the modular unit; an upper cover forming the upper side of the modular unit facing the ceiling; a tap-off branch for blowing air, attached to the suction box of the modular unit and permitting the injection of treated air into the interior volume of the modular unit; characterized in that same comprises a channel of articulated deflectors (10, 11) formed by an upper articulated deflector and a lower articulated deflector, attached to the peripheral frame at the level of the air blowing slot and allowing the blown air to be directed at a defined angle with respect to the ceiling varying from 0°, namely parallel to the ceiling when cold air is blown into the unit, to a maximum of 70° when hot air is blown into the modular unit; an thermostatic actuating means for actuating said channel of articulated deflectors via a means of actuating the deflectors (10, 11) such as an actuating rod and imparting to the channel a blowing angle dependent on the temperature of the treated air injected into the modular unit, said thermostatic actuating means comprising a piston the output stroke of which depends on the air temperature wherein said thermostatic actuating means is immersed, a return spring for exerting a force opposed to the stroke of the piston of said thermostatic actuating means and thus returning it to its minimum stroke when cold air is blown into the modular unit, and where said channel of articulated deflectors (10, 11) includes an articulated means for maintaining parallelism positioned in said channel and connecting the upper and lower articulated deflectors (11 and 10) to the articulation points B and C respectively, said upper and lower articulated deflectors (11 and 10) attached to the peripheral frame at the articulation points A and D defining together with the articulation points B and C of said articulated means for maintaining parallelism, a parallelogram A-B-C-D imposing a parallelism of the opposite sides thereof, and where said modular unit further comprises a connecting tap-off for air intake attached to the upper cover of the modular unit and communicating with a suction box provided with a filter sucking up ambient air from the upper cover of said modular unit.