Dec 07, 2016 - 10:03 AM
Typically, a 3 light fly light will attract flies from fairly far away. The limiting factors are usually walls and line of sight. If the flies can see it, they can be attracted from up to 100 feet away. This would be in a dark environment such as a night. During the day the line of sight is reduced due to daylight and lighting, but it can still be effective from many feet away.
Some cities and institutions such as ABI and the USDA have requirements on how many fly lights are required.
There is no set number of square feet. Again, it's purely line of sight for the fly. My recommendation is 1 per room in commercial restaurants, bars, bakeries, etc.