What's HEPA and ULPA Filters and Comparision?

Guide to Air Filters: HEPA vs. ULPA Filter

What is HEPA and ULPA Filter?

HEPA Filter - High Efficiency Particulate Air Filter, is a mechanical air filter that traps very small particulate matter. It traps harmful particles by forcing air through a fine mesh, and has a removal efficiency of more than 99.7% for particles with a diameter of 0.3μm (1/200 of the diameter of a hair), making it the most effective filter for pollutants such as smoke, dust and bacteria.

The ULPA Filter - Ultra Low Penetration Air Filter, is an air purification device with extremely high filtration efficiency. It can filter out particles of 0.1 to 0.2 μm in size, dust particles such as smoke and microorganisms, and its filtration efficiency reaches more than 99.999%.

HEPA and ULPA Filter Working Principle
Both HEPA and ULPA Filters are designed to trap very small particulate pollutants in the airflow by forcing air through a fine mesh. It usually consists of a continuous stack of subglass fiber membranes folded back and forth to form a wavy gasket to hold and support the filter boundary, and the fiber diameter is between 0.5 and 2 microns.

HEPA Filter
HEPA Filter refers to high efficiency particulate air filter, which can remove more than 99.7% of particles with a diameter of 0.3 microns. It is considered as the most effective filter medium for pollutants such as smoke, dust and bacteria.

ULPA Filter
ULPA Filter refers to Ultra Low Penetration Air Filter. The density of ULPA filter is more compact than that of HEPA filter and the filtration efficiency is also higher. It has a filtration efficiency of more than 99.999% for 0.1-0.2um particles, smoke and microorganism.

Application of HEPA and ULPA Filter
HEPA and ULPA filters are commonly used in purification units or piping ceiling modules installed in a pressurized chamber of clean room. HEPA or ULPA filters are also often used in equipment such as biosafety cabinets (BSC), laminar flow hoods, closed glove boxes, closed-loop filtration bins, and pipeless fume hood.

Advantage and Disadvantage of HEPA and ULPA Filter
(1)ULPA filter has a higher filtration efficiency than HEPA filter because of its more compact filter material structure
(2)ULPA filter allows less air to pass through the same area as HEPA filter, so more ULPA filter is needed to achieve the same air change rate.
(3)ULPA filter has more resistance than HEPA filter, so it needs to be used with more powerful fans and the cost is higher.
(4)ULPA filtration is more efficient than HEPA, so it is easier to clog and needs to be replaced more frequently.

How to choose between HEPA filter and ULPA filter?
Generally, HEPA filters are preferred in cleanroom requiring ISO5 to ISO8(Class 100 to 100,000 of FED STD 209E), since the use of HEPA filter at this level can meet the requirements at a lower cost and longer service life. ULPA filters are applied in cleanroom with higher cleanliness requirements or in cleanroom with more stringent control requirements for fine particles, which has better protection.