Final filters are designed to remove very fine particles from the air stream. They can range from 65% Bag filters up through 99.99999% ULPA & HEPA filters. While lower efficiency filters are designed to keep the HVAC system clean and operating efficiently, final filters are designed to remove specific sized particles from the air stream for health or design reasons. Higher efficiency filter are often used in applications that require a specified degree of cleanliness for either a medical or manufacturing process.