Your building has several intake areas which allow air to enter inside your building. Each intake is equipped with a mesh screen that allows air to flow while keeping out any organic or inorganic materials from coming along. If these screens aren’t properly taken care of they can easily become blocked, preventing fresh air from coming into your home.
For the most part, you can clean leaves, lint and other debris in minutes using a brush and/or a vacuum. Keep an eye out for any tears or breakages in the mesh screens. A broken mesh screen will allow larger particles to pass into your intake pipes, potentially creating problems down the line.
If you’re using a newer hot water tank, there may be a screen underneath it, which can also be cleaned using the same method.
It’s also worth noting that even during the cold winter months it’s important to keep these vents clean, even though they might bring in the cold outdoors. Keeping them clean and making sure that nothing is blocking each vent intake and outtake will help to keep you home well ventilated; especially when the rest of your home is shut up tight.