You could use the Gilbert 601T The Done Light Trap. You may just need to replace the glue boards more often if there is a lot of dust in the air.
According to the manufacturer, the general rule of thumb has been to space large traps such as the Gilbert 601T The Don Light Trap every 40 feet around the inside perimeter wall. If you multiply 40 x 40, you get 1600 square feet. However, the number of traps required will vary with the type and condition of the facility and the extent of the problem. If your building is next to a cow pasture, an unkempt dumpster, or if there are several cracks and crevices you may need more then one every 40 feet.
The Gilbert 601T is designed mostly for interior uses or in exterior areas where the trap is covered from the weather and not in direct competetion with other main light sources. This unit does not use a glue board. Flies are lured in by the light and killed instantly when they contact the light.
The Gilbert Fly Light Trap - The Don (601T) uses 2 two 40-watt Sylvania F40/350BL/ECO bulbs per unit.