DUCTING & GRILL WORK
The openings that connect to ducts and other spaces for the returning air are normally covered with grillwork.Every cooling or heating system will have air being pushed though into rooms and spaces through a system of ducts. This increases the air pressure in the conditioned area and at some time will act to even prevent any further air from entering unless a circulating system is set up to relieve the pressure. This is done normally through return ducts which allow the air to be recirculated or completely vented to the outside in certain cases. A grill will cover such ducts, and can also act to regulate the flow of air. They also act to close off the ducts from view. A return air grill also has a filter mounted on it to trap particulate matter and thus ensure that the recirculated air is more pure. This can also in the long run reduce the amount of cleaning required for ducts.