Instructions:Open the battery case, put in 2 * AA batteries, and close the case.Press the power button and a 9 second countdown will appear.The display will then flash a "C", at which point you can exhale evenly into the air intake for 3 seconds.After a beep, the result will be displayed, the result will be displayed for 5 seconds, and it will automatically shut down.If you want to test it again, just press the power button again.Features:Advanced semiconductor sensor, high sensitivity, fast response, easy to use.It will show the final test results in numbers and cartoon mode, everyone can check by themselves with this tester.5-level results: very good, normal, not very good, poor, very poor.Digital LCD and orange backlight cartoon instructions, energy saving and environmental protection, soft colors do not hurt the eyes.Quick response and recovery, with self-test to show different situations.Portable design, small size, compact structure, easy to put in your pocket and carry with you.Non-contact design, 5-10mm away from the detector, more hygienic.Power saving design, low battery indicator, 2 AAA batteries provide longer usage time (battery not included).