Before electric bulbs were introduced, oil candles were commonly used in the Ottoman times in Mosques. Hanging glass containers would be filled with olive oil and each container would have a wick to be lit one by one by hand.
Smoke coming out from these oil lamps would make the walls dirty. However, architects thought of making small holes in various corners of the buildings so that an air-circulation would be created and smoke would be taken out through those holes.
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