Twenty subjects will be accrued in three groups based on smoking habit: 10-20, 20-30 and >30 cigarettes/day. Eligibility criteria include male and female cigarette smokers ≥19 years of age, who are able to give informed consent, able to exhale into Eco Screen instrument for 15-20 minutes. All must be willing to make a serious quit attempt and be willing to use nicotine replacement therapy.