This baffle filter is manufactured from aluminium. It functions by forcing grease-saturated air to quickly and repeatedly change direction as it rises through the filter. Because the grease droplets cannot change direction as rapidly as the air carrying them, they end up condensing to the metal blades and then subsequently draining into the filter tray.
This method drastically reduces the risk of spreading flames should a fire break out on the cooking surface below. Additionally, because grease is filtered into a tray, there is no build up which would hinder airflow and function over time.