sand blasting slow

how old is the media? I run the sand blaster in my work shop daily. i run 80 grit aluminum oxide. after time it turns to a very fine powder. i change mine often. also it is very important that you have clean DRY air coming in. any moisture in the air will clump up the gun and will stop pulling media. some times i take the suction tube off the gun and blow air back thru it to clear the hoppper.