I noticed that I didn't catch a chest cold as I usually would have this winter.
Then I realized it was because I had taken 650 mg quercetin dihydrate daily. Quercetin also gives me energy.
My current capsule has only 250 mg and that might even be enough. Most quercetin products come with bromelain.
A person had really bad chest congestion and they started taking a Quercetin 250 mg tablet that had Ester-C and Bromelain daily and three weeks later their congestion is apparently gone.
For a year or two or more I would try quercetin for any lung or sinus problem like asthma, emphysema, COPD, pneumonia, bronchitis, sinusitis, etc.
The best value of quercetin that I know of is a 400 mg quercetin per capsule dose made by a major brand. It's actually listed as 800 mg quercetin with bromelain but that is for 2 capsules.