Research by Aberdeen University and the anti-smoking charity Ash Scotland saw monitoring devices placed in the homes of parents with children under the age of six.
The devices detected poor air quality within properties long after the mothers and fathers had stubbed out their cigarettes.
The Refresh project, which aims to reduce children’s exposure to second-hand smoke, reported that many mothers expressed surprise at the high levels of tobacco smoke measured in their homes.
The parents were also surprised that smoking in a different room or beside an open door or window gave less protection than they had assumed.
“With more than 85 % of cigarette smoke invisible to the human eye, it can be difficult to know how much smoke our children are breathing in the home,” Dr Sean Semple of the University of Aberdeen said.
“This study shows that measuring smoke in homes can help parents understand just how much is present and for how long it lingers in the air.”