When you actually think about it, the risk of inhaling a food particle also exists when you just breath through your mouth (while exercising or sleeping or doing whatever). When I use the nebulizer my teeth and mouth are closed tightly around the mouthpiece and I don't see how food can get through that space very easily. On reflection I don't think it is a huge worry otherwise aspiration pneumonia would be more common among nebulizer users and mouth breathers. Maybe I'm naive.