You can remove hardened lint from your dryer filter with a scrub brush. Gently scrub at the filter to remove the lint. Vacuums work just as well to remove hardened lint. Use your vacuum brush attachment and run the brush back and forth until the vacuum has sucked up all of the lint. You can also use a butter knife to pick away hardened lint.
Clean your lint filter after every use, the U.S. Consumer Product Safety Commission recommends. This prevents buildup and ensures that your dryer runs efficiently and safely.
Lint buildup on your dryer filter is a problem known to cause fires, because it blocks the flow of hot air and provides combustible material. Removing hardened lint is essential to prevent fires.