There are many manufacturers of kitchen fluorescent lights, and each manufacturer designs the diffuser box to mount to the ceiling in different ways. The same manufacturer could even design a different way a fluorescent box opens within their product line. Carefully studying the fixture can help you discover how the kitchen fluorescent light box opens. Be careful when replacing fluorescent tubes. The tubes have mercury and argon gas under pressure that could cause them to explode if you drop them or hit them against something.
Look on the ends of the kitchen fluorescent light fixture diffuser box.
Find the screws located in each end and turn the screws counterclockwise to remove them.
Carefully lower the diffuser box from the ceiling, exposing the fluorescent fixture.
Look along the bottom of the box around the kitchen fluorescent light for a single screw along the edge.
Remove the screw by turning it counterclockwise.
Carefully lower one side from the bottom of the box holding the light diffuser.
Place both hands against the light diffuser on the bottom of the box around the kitchen fluorescent light.
Push the diffuser up toward the light bulbs; be careful not to push too hard against the bulbs.
Tilt the diffuser at an angle, and wiggle it from the box.