The big air consumer was the Bag House/dust collector/vacuum cleaner for the plant. 350 - 7" x 15' filter bags in rows of 10. Collecting the dust from the plant and supplying 70% the combustion air for the burner/dryer. 250 horse driving a fan 3' w x 6' d for the vacuum. Each row had a 1 1/4" pipe with 10 3/8" holes centered over the filter bags below to knock the dust off the bags so it could be returned for use in the AC and continue to supply that necessary vacuum. Every 15 seconds 7 of those 1 1/4" valves opened for about 5 seconds.