Exhaust 100 Exhaust Louvres Available in flange and channel frame options. This louvre (louver) is designed to offer very high free areas and is most suitable in exhaust applications to provide very low pressure drop. * Free Area % Chart Louvre Widths: 0.300 to 0.900 - 1.000 to 2.500 * Free Area m2 Chart Louvre Widths :0.300 to 0.900 - 1.000 to 2.500