The fermentation lock or airlock is a device used in beer brewing and wine making that allows carbon dioxide released by the beer to escape the fermenter, while not allowing air to enter the fermenter, thus avoiding oxidation.
Most wood blinds are treated with a special finish to repel dirt and stains. Wood blinds can be cleaned with a good quality furniture polish and a soft cloth or clean sock. Spray the furniture polish on the cloth and wipe each slat individually. Avoid touching the cords. For heavier cleaning, you can use plain water, but be careful not to saturate the wood.
And, place outdoor furniture far enough away that sparks will not damage it. Using a screen for protection from the wind will prevent sparks from flying out as easily. And, to err on the safe side, do not use your fire pit at all when it is windy.