A filter is placed inside the vacuum behind the bag and before the motor for extra protection of the vacuum in case the bag is torn. The second filter is placed at the air outlet and at the back of the vacuum cleaner. The HEPA category is highly efficient and captures 99.50% of the microscopic particles present in the home environment. It filters the dust from the air that the vacuum cleaner emits and ensures a clean environment. If your vacuum cleaner does not have such a filter, then you can put a simple filter.