My garage has a ceiling with fiberglass insulation over plastic air spacers leading to vents under the roof shingles. There is no plywood or drywall over the insulation. The walls are insulated and finished. The soffit vents are pulling in the smell for about 3 weeks every spring. I wondered if i could just seal off the soffit openings. Maybe the vent spacers are too small to vent the air from the soffits, and the rest gets pulled back into the garage. I didn't want to go to the trouble of putting up ceiling plywood.The center part of the garage has no ceiling aboveit and is open to the attic part of the garage.