These fixed Grade-D filtration systems are designed to provide breathing air for a specific number of workers. The system filters inlet air to provide respirator users with Grade-D quality air. The first stage element filters bulk water and particulates; the second stage coalescing filter removes atomized oils and ultra-fine particulates, and the third stage removes organic vapors and odors. Filter change indicators are standard on all three filtration stages. Filtration efficiency is 99.99% at .01 microns. A built in carbon monoxide monitor operates on a 9-volt DC and/or 115 VAC for continuous detection. A high intensity audible alarm and light signals the workers of high CO content in their breathing air. A 115 VAC electrical conduit box is provided as standard. Auto-Air Option: If IDLH conditions exist, order a filtration panel with the Auto-Air option installed. This version automatically switches to a reserve bank of air cylinders to maintain full system air pressure to the workers.