Let’s get this out of the way first – the correct spelling of gnats is GNATS. Over the years, I have seen nats, knats, kats, nagts, nahts and ants. Yes, ants… But no, it is just gnats. The “g” is of course silent. In commercial spaces, fungus gnats are almost always associated with plants. Not always, mind you, but almost always. I’d say somewhere in the 90% range. Fungus gnats breed on microscopic fungi growing within the soil of a potted or atrium plant. In rare cases (think of the other 10%), fungus gnats may be breeding from mold and mildew associated with a moisture issue or water leak. To rid your space of gnats, do not turn towards pesticides. Seems odd that a pest control service provider would tell you NOT to use pesticides, but it is true. Fogging agents and spray pesticides will do little to control these pesky pests. They may kill off some of the adults, if you can get the adult gnat to come in contact with the pesticides, but the larva will continue to grow and within a relatively short period of time – adults will emerge and you will be right back to square one.