Use a screwdriver to loosen the screws securing the vent grates to the wall, ceiling or floor. Remove the screws and take the vent grates off. Place the screws in a plastic zip bag to avoid losing them while you clean the vent grates.
Pour 2 gallons of hot water into a large bucket. Add 2 quarts of white distilled vinegar to the water.
Soak the vent grates in the vinegar solution to loosen the greasy film and deodorize the surface. Leave the vent grates in the diluted vinegar for at least 30 minutes.
Remove one grate at a time from the vinegar solution. Sprinkle baking soda onto a damp sponge.
Scrub both sides of the vent grate to remove nicotine stains and smell. Use an old toothbrush to clean in between the grates, if necessary. Repeat soaking and scrubbing steps to clean all grates.
Rinse the vent grates with warm water. Lay them on clean towels to air-dry completely.