If my child is 10 months old, how much Mucinex (guaifenesin) should I give him for chest congestion with no fever?

Cough medicines. It is recommended not to give cold or cough medicines to infants and children less than 6 years old because they are ineffective in what they are supposed to help. Maintaining good hydration and providing good humidification either in the air or in the nose are all you need.