Do not use the breath analyzer until it has been 20 minutes since the last drink; please wait at least 3 minutes to begin next test after last test.The Alcohol Tester quickly and accurately tests for the presence of alcohol in the blood and encourages you to make smarter decisions about driving after drinking alcohol. Simple on / off button for operation. Insert hygienic mouthpiece, blow off and check the measured value. Easy to read digital display.2pcs AAA alkaline batteries last for 1 year standby. Each time you install batteries, you can test more than 200 times. Moreover, it is designed with low power indicationIf the instrument encounters a high concentration of alcohol gas, it is recommended to test it after 10-20 minutes. It is possible that the alcohol gas remains in the chamber, causing inaccurate tests. Please wait until the alcohol gas has dissolved. Or warm up 3 to 5 times to clean the sensor. Press the power button again and try again.