Why do hundreds of flies appear in a room?

Hundreds of flies can appear in a room due to factors such as food waste, garbage, or decaying organic matter that attract them. They can also enter through open Windows or doors, especially in warmer months when they are more active. Additionally, if there is a breeding site nearby, such as a compost pile or animal waste, it can lead to an influx of flies. Proper sanitation and sealing entry points can help prevent their presence.