Developing and Testing Health Warning Labels on the ENDS Device

Inclusion Criteria:

* Generally healthy individuals (determined by physical examination).
* Age of 21-35 years.
* Is willing to provide informed consent.
* Is willing to attend the lab as required by the study protocol.
* ENDS users (defined as using ENDS either daily or occasionally in the past 30 days)
* Have abstained from ENDS use for 12 hours prior to each session.

Exclusion Criteria:

* Report smoking cigarettes regularly (\> 5 cigarettes/month in the past year).
* Report regular use of any other tobacco/nicotine product (e.g., e-cig, pipes, cigars) in the past year.
* Women who are breast-feeding or test positive for pregnancy (by urinalysis at screening).
* Individuals with self-reported history of chronic disease or psychiatric conditions.
* Individuals with history of or active cardiovascular disease, low or high blood pressure, seizures, and regular use of prescription medications (other than vitamins or birth control).
* Individuals that report the use of non-commercial (i.e., street) e-cigarette liquid or products
* Individuals that report current EVALI or COVID-19 related symptoms (i.e., cough, shortness of breath, chest pain, nausea, vomiting, abdominal pain, diarrhea, fever, chills, or weight loss)
* Individuals that have or have been exposed to COVID-19 in the last 14 days.