sentences:  Similar to an air curtain to separate indoor air from outdoor air, for instance in restaurants and walk-in refrigerators, a powerful air curtain can defeat the chimney effect of the incineration process to eliminate any smoke from a brush incinerator.The air curtain acts as a lid on the process, and forces the smoke back into the fuel bed for a cleaner burn.Like all active systems of any type, a mechanical failure can result in total failure of protection.