How long is acute bronchitis contagious for?

It is not contagious: Acute bronchitis is a reaction to a viral respiratory infection (vri) by suseptible indiviuals, leading to frequent cough, increased mucus production, chest tightness, wheezing. Less than 20% of the population over react to the irritation of a vri with symptoms noted previously. The underlying vri is contagious for 24 hr before the onset of symptoms and for about 5 days after the symptoms begin.

Days to weeks: Depends on the causative organism, or if the pt has been a chronic smoker then it may be a inherent tendency to have generally inflamed airways without any infection and hence not being contagious.