In case you were not aware, storm (screen) doors usually have pneumatic pistons to prevent the door from slamming shut. You might notice that they slam part of the year or close very very slowly. There is actually an adjustment on most of them. It will either be a screw in the end or a little ribbed dial.

Above are two variants, both with the screw in the end. It is easier to see on the white piston. You tighten the screw to make the door close more slowly. You loosen the screw to make it close faster.