Abstract: A filter apparatus includes a filter panel having inner and outer surfaces and a configuration for completely covering a computer housing ventilation opening. The filter apparatus includes an adhesive layer permanently adhered to the inner surface of the filter panel. A thermochromic region is positioned on the outer surface of the filter panel which changes color as temperature increases. The thermochromic region includes an ink layer and a wax layer positioned atop the ink layer. The wax layer includes a thermochromic dye having a color different from the color of the ink layer. The color of the thermochromic dye blocks the color of the ink layer at an ambient temperature and is transparent to allow the ink layer color to be seen at an activation temperature. Therefore, the filter apparatus provides an indication when the filter is full and heat is building within the housing as a result.

Abstract: A filter apparatus includes a filter panel having inner and outer surfaces and a configuration for completely covering a computer housing ventilation opening. The filter apparatus includes an adhesive layer permanently adhered to the inner surface of the filter panel. A thermochromic region is positioned on the outer surface of the filter panel which changes color as temperature increases. The thermochromic region includes an ink layer and a wax layer positioned atop the ink layer. The wax layer includes a thermochromic dye having a color different from the color of the ink layer. The color of the thermochromic dye blocks the color of the ink layer at an ambient temperature and is transparent to allow the ink layer color to be seen at an activation temperature. Therefore, the filter apparatus provides an indication when the filter is full and heat is building within the housing as a result.