The answer to 'vacuum dusty' is that a vacuum that is not picking up dust and debris effectively is likely due to a few common issues. The vacuum filter may be clogged, the vacuum bag or canister may be full, or the vacuum head may have a blockage or not be making proper contact with the floor.
First, check the vacuum filter and clean or replace it if necessary. A clogged filter can significantly reduce suction power. Next, check the vacuum bag or canister and empty it if it is full. A full bag or canister will also limit suction. Finally, inspect the vacuum head and clear any blockages or check that the head is making proper contact with the floor surface. If these basic troubleshooting steps don't resolve the issue, you may need to call a professional vacuum repair technician to further diagnose and repair the vacuum.