The present invention relates to a method and device for the purpose of filtering particulate laden air exiting a rooftop from a commercial kitchen or other high particulate laden air exhaust. By positioning a filter at a distance from the air exhaust exit in such a manner that the air flow is reflected off the filter a substantial portion of the particulate matter is filtered out of the air without substantially obstructing the flow from the exhaust preventing problems that might be caused from creating back flow in an exhaust system.