There are actually two separate science fairs with separate judging and awards. Only exceptional entrants from the Senior Science fair are eligible to go on to the International Science and Engineering Fair. Designing the Project. The design of the experiment is the most important part of your project. Try to keep the number of things outside your control to a minimum.
Originality is very important.
That may be an idea for a project, but testing public restroom doors for harmful bacteria is not an original idea. You could try testing something ELSE, however. People expect public restroom doors to have bacteria, but there are other things they don't expect bacteria on. If plastic sandwich bags were tested, that would be original. This would be especially interesting because these are designed to be in contact with food.