The tester is powered by two AAA batteries. Batteries are not included. Instructions: 1. Press the power button to turn the tester on. It will beep once. The warm-up symbol will show up followed by a countdown from 10. 2. As soon as the “blow” symbol appears the tester is ready for use. Blow into the inhaler opening for 3 to 5 seconds. 3. The result will show up on the display.