The answer to 'my vacuum is filthy' is that a dirty vacuum can be caused by a variety of factors, including not emptying the dust cup or bag regularly, not cleaning the filters, and using the vacuum on carpets or floors that are excessively dirty. Symptoms of a dirty vacuum include reduced suction power, visible dirt and debris in the canister or bag, and poor cleaning performance.
To address a dirty vacuum, start by emptying the dust cup or changing the bag if it's full. Next, remove and clean any filters according to the manufacturer's instructions. You may also need to use a vacuum cleaner brush or crevice tool to remove built-up dirt and debris from the interior of the vacuum. If these basic cleaning steps don't improve the performance, it may be time to take the vacuum in for professional maintenance or repair.