It depends on what you are treating for and how bad the problem is, but you typically mix 1 to 10 ounces per gallon of water depending on severity of the problem, and each gallon of Essentria IC3 will treat 500 to 1000 sq ft. If we average this out, then a gallon of product can treat between 10,000 - 25,000 sq ft. For specific instructions, please read the Essentria IC3 product label.
Unfortunately, you are past the time to treat your home for cluster flies. Cluster flies enter your home in the late fall, early winter, usually around late September/early October. The flies enter through cracks around windows and doors and under siding. As the weather warms up or as your heat kicks on, the flys will emerge. Most will go outside but some will be confused and end up in the house. Next year, you should treat the outside of your home earlier in the year to prevent entry. For now, you can spray the inside of the home to help kill flys that are still in the wall. If you spray baseboards, window sills, etc you will kill the flies as they come out. As far as the flies that are in the house already, I would suggest our CB PCO Fogger with Pyrethrin. It should kill any that are flying around in the room you set the bomb off in. Be sure to read all directions and vacate the property for a few hours after setting it off.
You can also help by creating a "tick safe zone" in your yard. You should have an area that is at least 9 ft wide between your yard and any wooded area. Trim back trees to allow as much sunlight as possible into your yard. Keep grass as short as possible. Remove as much leaf litter as possible. A clearly defined, well manicured border between your yard and any wooded areas or weedy lots will reduce the chance of ticks infesting your yard.
Essentria IC3 can be used in a thermal propane fogger for indoor appliations only. Please refer to the Essentria IC3 product label for complete usage instructions.