Me and my buddy are pretty much daily smokers. Now i smoke around the same amount as he does. Over the past year or so he has developed phlegm in which he coughs out, and it contains like black or grey little pieces in it... He has asthma, and his dad smokes like a chimney (in the basement away from everyone). He stopped smoking all together, and started vaping... Is this from holding in hits? Is it from exposure to cigs? ... Does anyone else have or heard or this? What could that black/grey material be?