Abstract: The invention relates to a portable air cleaner unit which includes a casing having an air inlet and an outlet and defining an air cleaning path between the inlet and outlet. A prefilter is disposed downstream of the air inlet and a main filter is disposed downstream of the prefilter. An air mover such as a fan is disposed downstream of the main filter, and an exposed negative ion source is disposed downstream of the fan on the external surface of the air outlet. In accordance with the invention, the main filter consists of fibers shredded from a non-carcinogenic plastic membrane which has been permanently electrostatically charged. The negative ion source ionizes the cleaned air as it leaves the cabinet.