EPA Method 9 for visual opacity observation specifically excludes water vapor from the opacity measurement. The point for opacity determination is at the first point beyond condensed water vapor plume, or about 6 inches above stack exit if no water vapor is present. Opacity measurement before...
Stonecold's method may be acceptable in the case of a plant-wide emissions cap, but in determining specific emissions for a process/emission unit it may not provide the level of detailed information a regulatory agency would typically accept. Your intial thought of a material balance around the...