If they're iron powder, here's nothing you can do about it. A grill with holes small enough to keep iron powder out will keep the sound in. Any other problem should be covered by the warranty. (But if you work around construction sites of any sort, that's normally part of monthly maintenance - opening any device with a speaker and removing the iron powder. I used to spend 4 hours a day "repairing" two way radios used on a NYC building site, just pulling iron off the speakers.)