GRAIN OPERATIONS Oxygen and confined spaces are most difficult to control. This leaves eliminating ignition sources and controlling dust through material handling techniques and housecleaning as the important variables in eliminating dust explosions. the broad, generally accepted MEC for grain dust explosions is about 0.05 ounces per cubic foot of volume. They say that the optimum explosive concentration (OEC) is about 0.5 to 1.0 ounces per cubic foot - about 10 times the MEC. The OEC value of 0.5 to 1.0 ounces 48 " Scalperator 24 " - 112 " Wide of wheat flour per cubic foot equates to about 1.5 to 3.0 cubic inches of grain dust per cubic foot of air volume. The MEC would be about 0.15 to 0.30 cubic inches per cubic foot. A single piece of paper is about 0.004 inches thick, so it doesn't take long to accumulate enough dust to reach the MEC. Gallery floors commonly accumulate one-fourth to one-half-inch of dust in a week or two during harvest, and belt tunnel floors commonly accumulate this much dust when silos are being turned in July and August. Extra housekeeping is necessary during these times to keep dust levels below the MEC. OSHA regulations for grain elevators require that grain dust not exceed a 1/8-inch depth within 35 feet of a bucket elevator. Based on the above MEC values, keeping grain dust depths at less than 1/8-inch deep on any working floor of an elevator generally would not keep that facility below the MEC. The MEC concentration of 0.05 ounces per cubic foot (50 grams per cubic meter) is more than three times the OSHA standard for worker exposure (15 grams per cubic meter). An additional danger of having dust levels above the MEC involves visibility. Suspended grain dust at the MEC will obscure the visibility of other workers about 5 to 10 feet away. Having 0.05 to 0.10 ounces of dry grain dust or flour per cubic foot of