After being frustrated from wearing a respirator for literally hours, and still inhaling dust and paint through ill fitting masks, I made a fresh-air, positive-pressure respirator. The positive-pressure ensures that any leaks blows air out and doesn't allow fumes in.
I started with a new high quality paint mask capable of filtering dust, organic vapor, paint and pesticides. I converted the mask to positive-pressure by covering the filter cartridges with two rubber plumbing caps that have band clamps. I installed 1/4" barb fittings in each cap.
I then filter the air from my air compressor through an homemade air dryer and two particulate filters and plumb the mask into the air line with a standard quick connect fitting.
I made an air dryer by passing the compressed air through a copper coil of tubing, that is submerged in ice water. The air then flows into an air/water separator. The ice bath is effective in condensing the water in the air, thus allowing the air/water separator to function. Most air/water separators only remove liquid water. They are not effective in removing water vapor. The result is cool dry air to spray and breathe.
Hope it helps.