How close does baby need to smoking for it to be harmful SID?

It probably would not be even close to enough smoke to reach the amount of smoke a baby gets when the parents smoke. When they say smoking increases the risk that is when the mother or father smoke either in the house a lot or they always have the smell on their skin and clothes. So, I wouldn't worry about this effecting your little one. You would be surprised at how many times my daughter and I pass a group of people that are smoking, to where she breathes a little in, or people will actually light one around us!