The invention relates to an atomizer which is provided with a truncated cone chamber or two truncated cones connected through a base. Each truncated cone is formed by a series of POPOID (bendable and/or stretchable corrugation) sections, so that the chamber can keep the shape no matter in a stretching state or a contraction state in a spontaneous mode except the condition of applying internal pressure tending to expand the chamber. The atomizer is commonly used in mechanical ventilation.
