Abstract: A foldable filter comprising a pleated section, said pleated section having a plurality of pleats and where said filter is in its operating configuration, each pleat has an operating width (W) from an air direction facing tip of one pleat to an air direction facing tip of the next pleat which is from 5 to 10% of a pleat amplitude (A), where said pleat amplitude is from 15 to 30 mm, and wherein said filter comprises an adhesive melt on a portion of the pleat tips to prevent those pleats extending substantially beyond said operating width (W) and wherein the means for preventing a portion of the pleats from extending beyond said operating width is adhesive fixed to a plurality of air direction facing tips. The invention also relates to an air purifier comprising such a foldable filter, as well as the foldable filter in a folded configuration and a packaged foldable filter comprising secondary packaging.

Abstract: An air filter unit for purifying air. The air filter unit includes a filter body extending along an axis, a first filter frame and a second filter frame arranged on opposite ends of said filter body. Each of the first and second filter frame includes four elongated frame members turnably secured to each other. The four elongated frame members are turnably secured to each other such that the filter body could be arranged in a first and a second state. The first state is such that the filter body is folded to reduce the volume of the filter unit and the second state is such that the filter body is assembled.

Abstract: An air filter unit for purifying air. The air filter unit includes a filter body extending along an axis, a first filter frame and a second filter frame arranged on opposite ends of said filter body. Each of the first and second filter frame includes four elongated frame members turnably secured to each other. The four elongated frame members are turnably secured to each other such that the filter body could be arranged in a first and a second state. The first state is such that the filter body is folded to reduce the volume of the filter unit and the second state is such that the filter body is assembled.