A vent grille (also called a diffuser or register) is a type of ventilation component commonly found in heating, ventilation, and air conditioning (HVAC) systems, as well as in kitchens, bathrooms, and other areas of buildings where air circulation is important. It is made with a simple louvered structure that is designed to cover an opening in a wall or ceiling through which air can flow in or out. The primary function of a vent grille is to allow air to flow in and out of a space while preventing the entry of foreign objects such as debris, insects, or animals. Vent grilles may also be equipped with filters to remove impurities from the air, or louvers to control the direction and volume of the air flow.