Spirometry is a breathing test that can diagnose COPD on the basis of a measurement called FEV1 (forced expiratory volume in 1 second), which is the amount of air that a person exhales in 1 second compared with that of a healthy person of the same age and size. A person with an FEV1 of 60% exhales about 60% the amount that a typical, healthy person the same age and size exhales in 1 second. Spirometry can sometimes find COPD in people who do not know they have the disease. For this reason, some people wonder whether doctors should include spirometry as part of routine preventive health care.