To prevent black fiberglass tissue from becoming dirty, follow these steps: 1. Regularly clean the surface with a soft brush or cloth to remove dust and debris. 2. Avoid direct exposure to harsh chemicals or substances that can stain or damage the fiberglass. 3. Use a protective cover or shield when working in areas where dirt or debris is likely to accumulate. 4. Apply a protective coating or sealant specifically designed for fiberglass to create a barrier against dirt and stains. 5. Regularly inspect the fiberglass for any signs of damage or wear, and address these issues promptly to prevent further dirt accumulation.