the diffuser attachment of the invention fits onto the nozzle portion of a hair dryer and diffuses the stream of air emitted therefrom over a large area so that air is emitted from the diffuser in a gentle stream which does not disturb the hair . hair is substantially not blown around when using this diffuser attachment , as it is when using a regular hand - held dryer without a diffuser attachment . problems occur with known diffusers in that hot air tends to get trapped within the diffuser and the dryer overheats causing the motor to cut out . using the diffuser attachment of the invention , the slots around the sidewall draw cool air into the diffuser , which is emitted with the hot air from the nozzle while the dryer is in use . the same slots serve as exhaust slots for hot air remaining in the diffuser when the hair dryer is turned off . the face plate of the diffuser is substantially larger in area than the nozzle of the hair dryer , and may , for example , have a diameter between 2 and 6 times that of the nozzle of the hair dryer . referring to the drawings , in which like numerals represent like parts , fig1 to 4 show diffuser attachment 2 attached to nozzle portion 4 of a hair dryer ( shown in broken lines ) which is inserted at inlet end 6 of diffuser attachment 2 . diffuser attachment 2 has a hollow body which is preferably circular in cross section and has an outer surface 8 forming a sidewall in which a plurality of openings , such as slots 10 , are positioned . outer surface 8 may have a portion 12 of smaller diameter and a rim portion 14 for receiving face plate 16 . face plate 16 is attached to the outlet end by means of screws 18 , or other appropriate means . face plate 16 has a plurality of perforations 20 which may be round , elongated , or other appropriate shape , of various sizes and arrangements known to one skilled in the art . details of end portion 6 of diffuser attachment 2 are shown in fig3 and 4 . hair dryer nozzle 4 enters a cavity in the end of diffuser attachment 2 . the cavity is formed by flexible finger portions which enable the diffuser attachment to be held firmly on the hair dryer nozzle . in a non - limiting example , shown in fig3 and 4 , end portions 22 of the fingers extend inwardly from the inner circumference 24 of the diffuser attachment , extending substantially diagonally a sufficient distance to form an entry passage for the hair dryer nozzle . finger portions 28 then extend longitudinally of diffuser attachment 2 . these finger portions 28 terminate in finger portions 30 each of which is substantially perpendicular to portion 28 from which it extends . finger portions 28 are held together by resilient elastomeric retainer band 32 , which may be a rubber or plastic retainer known to one skilled in the art . clips 34 may optionally be used to hold the resilient retainer in place on the finger portions . clips 34 are suitably formed by partially cut - out portions from finger portions 28 , attached to finger portions 28 at one end . a layer of filter material 36 is preferably located behind face plate 16 for trapping dust . filter material 36 is preferably cellular sheet material , such as a sheet of foamed plastic . ventilation slots 10 extend around the sidewall of the diffuser attachment for minimizing heat buildup and reduction of back pressure in the hair dryer . the ventilation slots may optionally extend through shoulder portion 26 which separates surface portions 8 and 12 of the diffuser attachment , as shown in fig1 and 3 . an alternative embodiment of the diffuser attachment is shown in fig5 and 6 , in which fig5 shows a diffuser attachment 38 , similar to diffuser attachment 2 ( shown in fig1 to 4 ), wherein slots 40 are spaced apart parallel to each other around attachment 38 , and substantially perpendicular and adjacent to face plate 42 . diffuser attachment 38 has a substantially cylindrical hollow body which flares out at its outlet end to meet substantially enlarged face plate 42 . face plate 42 is held in position by screws 44 and filter material 46 is positioned behind face plate 42 . ventilation holes 48 and 50 , shown in fig6 serve the same function as ventilation holes 20 in fig2 . ventilation slots 10 in fig1 to 4 and slots 40 in fig5 and 6 allow cold air to be pulled into the diffuser attachment , similarly to the principle employed in a jet engine or in a ducted - fan engine . the movement of the peripheral air into the diffuser attachment eliminates the reduced air flow into the outside corners of the attachment which would normally create back pressure , generally the major cause of overheating and cycling in a hair dryer . slots 10 and 40 further allow internally trapped hot air to vent from the diffuser attachment . when a hair dryer is shut off , the thermostat typically overshoots since air movement has ceased and the heater coil is still hot . the diffuser attachment provides a long extension to the nozzle of the dryer which , in conjunction with the diffuser structure , traps the hot air which contributes to the thermal overshoot . the peripheral slots 10 and 40 provide the necessary venting to eliminating this problem . other locations , shapes and sizes for slots 10 and 40 in the sidewall of the diffuser will be apparent to one skilled in the art . for example , the same function can be accomplished with vent holes 10 and 40 of different shape . an elongated slot - like shape is shown as a non - limiting example , but other shapes which serve the same functional purpose may equally well be used . slots 10 and 40 may be positioned adjacent the face plate as shown in fig5 or may be positioned in the sidewall spaced from the face plate , as shown in fig1 and 3 . the location is such that it results in cool air entering the diffuser attachment and hot air exiting the attachment to prevent overheating and eliminate cycling . in the diffuser attachment of the invention , the hollow body space between the face plate portion and the nozzle attachment portion is unobstructed , allowing free circulation of air within the hollow body of the diffuser and allowing air to flow freely through the apertures in the sidewalls of the hollow body portion . while the invention has been described above with respect to certain embodiments thereof , it will be appreciated that variations and modifications may be made without departing from the spirit and scope of the invention .