Sensitive polymer (2) reacts to ambient magnitudes to set, control or regulate a flow rate. No external energy is required. Preferred features: A membrane controlling flow rate of fluid and/or aerosol, is a sensitive polymer affected by specific ambient magnitudes. Consequently, flow rate is influenced by a volume and/or structural alteration. A filter similarly controlling flow rate includes a similarly sensitive polymer. A valve controls or regulates, using the same effect. The idea is extended to a two-or multichamber valve and a dosing unit for fluids and/or aerosols. This unit includes an (e.g. absorbent) body reacting to ambient magnitudes by delivering or accepting fluids and/or aerosols. A pump and reservoir can be conceived, using this action. Temperature-sensitive polymers are applied in this way, as are pH-sensitive polymers. Ion concentrations could be sensed, alternatively material concentrations, especially organic solvent concentrations. Organic materials, dissolved or otherwise, produce the effect. The polymer is sensitive to pollutant concentrations. The membranes comprise sensitive polymers moderating flow rates by alteration of their diffusion characteristics. The sizes of their perforations or pores change. The membrane may be coated with a sensitive polymer having this effect. The membrane may include sensitive polymer fibers or small particles. Several such membranes may be combined. A filter chamber is filled with a sensitive polymer in bulk volume-, fibrous- or small particle form. The absorbent sensitive polymer has a porous structure. Contraction or expansion of a sensitive polymer casing drives out the fluid and/or aerosol. A fluid and/or aerosol flow is caused by contraction and/or expansion in a reservoir. A similar effect is produced by expansion and/or contraction of a cross section of sensitive polymer through which the fluid and/or aerosol stream can flow. For increased dynamic response of the functional component, the sensitive polymer has a porous structure.