This bathroom ceiling fan has had the louvered cover dropped partially down to expose the fan itself. These get very dirty here in the Sonoran deserts of Tucson. Unplug the fan from the power, or open the appropriate circuit breaker to avoid shock. Use a vacuum cleaner with the small nozzle and the brush to clean these first. A soft brush will also help with the tight spots. Finish by carefully wiping down casings and blades with a cleaner that does not require rinsing. Finish removing the louvered cover and wash it in a sink. Let everythng dry, turn the power back on and the fan will look and work much better.