I have asthma, and it seemed that every time I went to WDW I would come home wheezy and have sinusitis, bronchitis or pneumonia within a few days. This time, I took a mask, used it *almost* every time I was near fireworks or special effects. I did go into a karaoke bar with some friends one night for about 1/2 an hour, had to leave and use my rescue inhaler once because of the smoke -- but that was the only time I had to use it on the whole trip. I really think the mask helped! I highly recommend it. I used the 3M 8511 with the little cool-flow valve. It was just a couple of dollars, worth every penny 
When we were at Fantasmic and Illuminations, the cloud of fireworks smoke came right at us - a few people around me were a bit jealous...

When we were at Fantasmic and Illuminations, the cloud of fireworks smoke came right at us - a few people around me were a bit jealous...