Abstract: An apparatus is provided for neutralizing the harmful effects of hazardous material stored within a rigid housing which might otherwise escape to the atmosphere. A cavity within the rigid housing receives the hazardous material. The cavity is airtight except for interior and exterior vents at the top of each of two double walled sides. A container holding a filter medium capable of neutralizing the toxic or harmful effects of the hazardous material is mounted within a chamber between each of the two double walled sides. The interior vents are connected into the containers so that any unconfined hazardous material within the housing passes through the interior vents into the filter medium. The exterior vents allow the neutralized material to escape to the atmosphere. Warning devices are inserted into the front of the housing and into the tops of the filter container chambers to provide an external visual indication of the presence of unconfined hazardous material within the housing and within the chambers.