Abstract: Technegas is a suspension of ultrafine ⁹⁹Tc^m labelled carbon particles produced in an atmosphere of high-quality argon. It is cheap,always available and easy to use,delivers a low radiation dose,and for the most parts,provides good quality lung images.In normal lungs,there was no difference radios in the lungs between Technegas and inhaled ⁸¹Kr^m、¹³³Xe.Compared with ordinary radioaerosols,it causees fewer and less intense foci of parasitic bronchial activity,and assures good peripheral penetration and alveolar deposition.And Technegas ventilation imaging also has many ad-vantages over other methods,such as X-ray examinations and bronchoscopy.