The twelve petalled center is called the Heart and is placed behind the sternum bone in the spinal cord. This center corresponds to cardiac plexus, which produces the antibodies till the age of twelve. The Heart chakra controls breathing by regulating the functioning of heart and the lungs.
When Kundalini pierces this center, the person becomes extremely confident, secure, morally responsible and emotionally balanced personality. Such person is very benevolent and loves humanity without any self interest involved and is dear to all.
Through deep and relaxed breathing, the air element can help relief tensions at the heart level.