A leading aggregate company in Southern Ontario was having dust issues in their sifting building and truck filling area. The dust problem was so bad inside the building you could not enter the building as visibility was reduced to zero. The truck filling area also had a dust issue. During the trailer-filling process, dust would billow out from the area.
The solution for the sifting building was to extract air from the building on the opposite side of overhead doors, exchanging the air once every four minutes, on a continuous basis. The truck filling area problem was remedied by enclosing the area and extracting air from the side at each silo, thus maintaining a slight negative air pressure within the loading area. The building required 40,000 cfm to exchange the air every 4 minutes, and by using auto blast gates on the building, when a truck is to be filled (a few times a day), the airstream of 40,000 cfm is redirected to the truck loading area.