A Comprehensive Evaluation of Tobacco-Flavored vs. Non-Tobacco Flavored E-cigarettes on Smoking Behavior

Inclusion Criteria: * \>= 21 years old * Smoke \>= 5 cigarettes per day for the past year * Willing to use either an EC or NRT * Read and speak English * Have a smartphone Exclusion Criteria: * Report currently using smoking cessation medications, NRT, or actively seeking treatment for smoking cessation * Current use of an EC \> 4 days a month * Diagnosed medical conditions of lung disease, asthma, cystic fibrosis, heart disease or chronic obstructive pulmonary disease (COPD) * Unmanaged (unmedicated and/or without counseling) diagnosis of schizophrenia * History of cardiac event or distress within the past 3 months * Currently pregnant, planning to become pregnant within 6 months, or breastfeeding * High blood pressure not controlled by medications * Serious angina pectoris or chest pain * Stroke within the past three months * Known allergy to propylene glycol or vegetable glycerin * Serious underlying arrhythmias, irregular heartbeat or abnormal heart rhythm * Live in same household as another study participant