Participants
SHOP
A total of 252 smokers in Canada participated in the study from July 2020 until June 2021, recruited by a research agency (aged 19 years and oversmoked factory‐made cigaretteshad smoked at least 100 cigarettes in their life‐timecurrently smoked 10 or more cigarettes a day on every day of the weeknormally purchased cigarettes in packs of 25used a brand or brand variant in which cigarettes were available in pack sizes of 20 as well as 25 in a shop convenient to themlived anywhere in Canada outside British Columbia, Northwest Territories, Nunavut and Yukoni
able to read and write sufficient English to complete all study procedureswilling to record on each cigarette pack dates when the pack was opened and when finishedwilling to send photographs for 4 weeks of their completed cigarette packswilling to purchase and smoke their usual brand variant in packs of 20 for 2 weekswere not pregnant or trying to become pregnantwere not intending to quit smoking in the next 3 monthshad not used e‐cigarettes at least weekly over the past month and intended to continue not doing sohad not smoked one a week or more roll‐your‐own cigarettes over the past month and intended to continue not doing sodid not normally transfer cigarettes into a caseusually buy their own cigarettesdid not live in the same household as someone who has enrolled in the study.