I've been using cup shaped paper ones with a single elastic band. I got them from Foy's or Siegel. I have a heavy duty one but it's very uncomfortable. I just ordered Dust Bee Gone http://dustbeegone.com/dustmask.html. I'll see how that works. There must be a good comfortable respirator out there that one can keep on all the time. Most of my day I spend with pigeons. My allergy is becoming a problem. Has anyone used a motorized respirator? I heard that they tend to be more comfortable.
You can pick up a douible filtered respirator from Home Depot . Just ask for the ones with the bio filters on them. I am in the restoration industry and use them all the time. Change the filters a few times a year. They work great and are better for YOU!