How do I use the timer to automatically shut off the air purifier?

Tap the up or down arrows to set the timer, and continue tapping to toggle through to the desired time — the timer can be set in one-hour intervals from one to eighteen hours. The digital display will count down and show the hours remaining, and the unit will automatically shut off after the selected run time. Do not use this option if you want the unit to run continuously. (Page 5)