Melamine is a common material used in shelves and cupboards in kitchens and laundry rooms. It's ideal because it's available in many colors, is typically less expensive than solid wood and easy to clean. The inner core of a melamine shelf is particle board, while the outside of the shelf is a hard, colored material. This part of the shelf is not painted, so using a paint stripper would prove futile.
If you've painted a piece of melamine yourself, you can strip the paint easily if you decide you don't like the finish and wish to change its color. The stripper you use should relate to the type of paint you used to cover the melamine shelf. If you used latex paint, for example, a paint stripper recommended for latex paint is most suitable. Mineral spirits are a useful solvent for stripping many types of paint.
Using any kind of chemical stripper exposes you to potentially harmless materials and vapors. When stripping paint off your melamine shelving, do so in a well-ventilated area, such as a garage. If you cannot remove the shelving from its location, open as many windows in the area as possible and use a fan to circulate the air. Wear rubber gloves when handling the stripper and take frequent breaks to avoid breathing in the solvent.
To repaint melamine shelving, scuff up the coating of each shelf prior to applying the paint. This process will allow the coat of paint to fully adhere to the melamine. Use 150-grit sandpaper, either by hand or with a random-orbit sander, to sand the entire surface of the shelving. You don't need to try to remove the melamine coating; instead, just give it an abrasiveness to which the new coat of paint can adhere.