Millions of children living in the UK are affected by smoking every day, even though they don't light up themselves.
Almost half of all children live in a house where they are exposed to tobacco smoke, according to the organisers of No Smoking Day, which is on 9 March.
The chief exective of the charity, Ben Youdan, told Newsround living with parents who smoke is the same as puffing on 80 cigarettes a year.
He added in Britain 450 kids younger than 16 start smoking every day.
More than 17,000 children younger than five are go to hospital every year because of passive smoking
Children whose parents smoke inhale the same as 80 cigarettes a year
10% of kids aged 11-15 are regular smokers
23% of regular smokers are younger than 15
450 children in Britain start smoking every day
No Smoking Day has been running once a year since 1984 and since then has already helped 1.2m smokers quit the habit.
And the charity says that 85,000 people will quit for good on No Smoking Day 2005, which is the same as every smoker in Manchester giving up.
In January a survey of kids living all across Europe found they were three times more likely to get lung cancer than children who live in smoke-free homes.