Secondhand smoke (SHS) caused by smoking on apartment verandas is a severe social problem in Japan. If someone smokes on a veranda, SHS drifts into other residents’ rooms through their windows. Most non-smoking residents are annoyed by this, but they do not confront the person responsible. To study this situation, we burned cigarettes and measured the spread of SHS in terms of fine particle (PM2.5) concentrations. Cigarette smoke generated on a lower veranda spread to upper and horizontal neighboring verandas and into rooms through windows, reaching a maximum concentration of 139 μg/m3. The Health Promotion Act that was revised in 2018 and enacted in 2019–2020 requires all smokers to avoid producing SHS, even outdoors and at home. It is expected that combining the measurement of SHS from verandas to other verandas and rooms with the revised Health Promotion Act could create a national consensus on “no smoking on apartment verandas.”
