An electronic cigarette, or e-cigarette, runs on a battery, either disposable or rechargeable. The airflow sensor senses when you suck in air from the mouthpiece. The sensor tells the microprocessor to turn on the heating element and start the process that turns the nicotine solution into a vapor that you inhale. Many e-cigarettes have an LED (tiny light) at the end that glows red when you inhale.
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