Peak flow meters

A peak flow meter is a pocket-size device that measures peak expiratory flow (PEF), or how much air a person can quickly breathe out. To measure PEF, the person takes a deep breath and then blows into a tube on the peak flow meter as hard and as fast as possible. A scale on the device shows how much air is breathed out. This can be done at home.

Peak flow meters come in many shapes and sizes.