|We used airflow covers, but I found that we had a smell that wouldn't go away with our mediums. I had no luck getting rid of the smell (not encouraging news, I know). I did try sunning them, making sure they were never stored with wet diapers and soaking in baking soda. It really didn't help, but the one thing I didn't try that I thought of now, I might have tried tea tree oil - just on a whim, I'm not sure it would work. I just moved up a size when nothing worked - my daughter was getting to the end of the mediums, so we went up a size early. Sorry that's not overly helpful, but you can try what we tried, and maybe it will at least improve it a bit. Good luck.