More than 80 per cent of second-hand smoke is invisible, odourless, and contains harmful cancer causing toxins, so no matter how careful you are children still breathe in the harmful poisons.
Around 800 children visit their doctor every day due to the serious effects of second-hand smoke exposure in homes and cars.
Nearly three-quarters of children worry that their mum or dad will die because they smoke.
That is why this week sees the launch of a campaign to encourage people to stop smoking in their homes and cars.
Exposure to second-hand smoke is a serious health hazard, especially for children who breathe more rapidly and inhale more pollutants than adults and there is no safe level of exposure.
New laws come into force on Thursday 1 October which will make it illegal to smoke when someone under the age of 18 is also in the vehicle.