Abstract: A lid and a method of testing a test substance in a porous membrane insert (PMI) are dis closed, the lid including a body, sidewalls positioned along an outer perimeter of the body and configured to be seated on a shoulder of a multi-well cell culture plate, and at least one hole through the body and/or at least one knockout, wherein the lid is configured to provide the at least one hole over a corresponding well of the multi-well cell culture plate which contains the porous membrane insert. The method is a method of testing a test substance in a PMI, the method includes the steps of providing a multi-well plate with PMIs, providing the lid, removing the cover from the multi-well plate, adding the test substance, placing the lid on the multi-well cell culture plate, and conducting a manipulation of the test substance.

Abstract: An vitro air-liquid interface (ALI) exposure of cultured cells makes it possible to examine the toxicological properties of the tested air. A method for evaluating effect of a polluting air stream comprises the steps of exposing cells to a membrane until adhesion of the cells has occurred, feeding cells periodically until there is a confluent monolayer of cells on said membranes, aspirating off non-adherent cells, applying fresh media, exposing the cells to over-head stream containing pollutants, removing the cells from the membranes that have been exposed to the over-head stream, then measuring the cells' response to toxins in the over-head stream.