Rationale

The current standard as written does not accurately represent wildfire conditions as it allows for testing of a sample vent that is mounted in either a vertical or horizontal position. Changing wind patterns and a variety of other factors can affect the direction of flame impingement upon the vent surface. There is also a significant heat flux disparity in this test method between a horizontal exposure and a vertical exposure. Data collected by Western Fire Center indicates a horizontal exposure (e.g., soffit) to be approximately 25 kW/m2, compared to a vertical exposer (e.g., foundation, gable) being approximately 75 kW/m2. Requiring both horizontal and vertical flame exposure tests for all vents regardless of their intended installation would help to address both concerns and make for a more accurate and uniform test. (see sections 4.3.1 and 9.2.2)