The peak flow test measures how fast you can breathe out after you’ve taken a full breath in. Your peak flow score is sometimes called your peak expiratory flow (PEF).
Take the biggest breath in that you can. Then blow out as fast as you can, into the small, hand-held plastic tube called a peak flow meter. You don’t need to empty the lungs completely – just a short, sharp blow, as if you’re blowing out a candle. The measurement taken is called your peak flow.
Each time you check your peak flow, you should do 3 blows, with a short rest in between the blows. The best of the 3 is the one that should be recorded.