What is the ruling on sitting with smokers during the daytime in Ramadan, and does that affect the fast?

A Muslim should not sit with smokers unless there is a necessity, especially if fasting. If he does sit with them, he must enjoin good and forbid evil. His fast is not invalidated by the smell of their smoke because it is impossible to guard against it. If dust, a fly, or smoke enters the throat of a fasting person by itself, without any action on his part, and he was unable to prevent it, then his fast is not broken by scholarly consensus.