What are HEPA and ULPA?

In clean rooms, biological safety cabinets, pharmaceutical workshops, semiconductor factories and other places that have strict requirements for air cleanliness, HEPA and ULPA are the two most core terminal air filters.

HEPA (High Efficiency Particulate Air) , the Chinese full name is high-efficiency air filter. HEPA refers to a filter that has a capture rate of more than 99.97% for particles with a particle size of 0.3 μm and an initial pressure loss of less than 245 Pa under rated flow conditions. HEPA is the most basic terminal filtration equipment in clean rooms and is widely used in ISO 5-9 clean environments.

ULPA (Ultra Low Penetration Air) , the Chinese full name is ultra-high efficiency air filter. ULPA is an upgraded version of HEPA. Under rated flow conditions, it has a capture rate of more than 99.9995% for particles with a particle size of 0.15 μm (some standards are 0.12 μm). The filtration accuracy of ULPA is much higher than that of HEPA, and it is suitable for ISO 1-4 ultra-high cleanliness environments.

To put it simply, HEPA is 'high efficiency' and ULPA is 'super efficient' - both are the 'last line of defense' for air filtration, but ULPA's filtration standard is two orders of magnitude higher than HEPA.

The core difference between HEPA and ULPA

1. Different filtration efficiencies

This is the most fundamental difference between the two.

Looking at specific data: HEPA's filtration efficiency for 0.3μm particles is over 99.97%, while ULPA's filtration efficiency for 0.12μm particles is as high as 99.9995%. Converted into penetration rate, HEPA allows 0.03% of particles to pass through, and ULPA only allows 0.0005% of particles to pass through - ULPA's penetration rate is only one-sixtieth of HEPA's。

2. Different grade standards

High-efficiency and ultra-high-efficiency filters have strict classifications:

HEPA usually corresponds to H13 and H14 levels, and ULPA corresponds to U15, U16 and U17. From 99.995% of H14 to 99.9995% of U15, it seems that there is only one level difference, but in fact the filtering accuracy has improved by an order of magnitude.

3. Different applicable scenarios

4. Different resistance and energy consumption

The higher the filtration precision, the greater the resistance when air passes through the filter material.

• HEPA initial resistance : about 150-220Pa

• ULPA initial resistance : about 200-280Pa

Under the same size, the initial resistance of ULPA is about 30% higher than that of HEPA. This means that FFU equipped with ULPA requires a fan with higher static pressure to overcome the resistance, and the energy consumption increases accordingly.

5. Different costs

The purchase cost of ULPA is usually 2.5 to 3.5 times that of HEPA. In addition, ULPA is usually replaced more frequently than HEPA. As long as the cleanliness meets the standard, higher levels are not always better - over-configuration will bring unnecessary cost burdens.

How to choose HEPA or ULPA?

When selecting, it is recommended to make a step-by-step judgment based on the following logic:

Step one: clarify the cleanliness level requirements

• Requires ISO class 5 (class 100) and below cleanliness → HEPA (H13/H14) is sufficient

• Ultra-high cleanliness of ISO Class 3 and above is required → ULPA (U15+) required

Step Two: Assess Process Sensitivity

• Semiconductor lithography, nano-manufacturing, aerospace assembly and other scenarios sensitive to 0.1μm particles → ULPA

• Conventional clean scenes such as pharmaceutical filling, hospital surgery, food processing, etc. → HEPA

Step Three: Weigh the Costs and Benefits

• Limited budget and moderate cleanliness requirements → HEPA is the cost-effective choice

• The pursuit of ultimate cleanliness and extremely high yield requirements → ULPA’s investment is worth it

Step 4: Consider System Matching

ULPA has higher resistance. Before choosing, you need to confirm whether the fan static pressure of the existing FFU or air conditioning system is sufficient. Otherwise, you need to upgrade the fan configuration simultaneously.

Common misunderstandings

Myth 1: ULPA must be better than HEPA. Not all scenarios require ULPA. H14 HEPA for ISO Class 5 (Class 100) clean rooms fully meets the standards. Blindly choosing ULPA will only increase procurement costs and operating energy consumption.

Myth 2: HEPA and ULPA are interchangeable. The two have different resistances, and direct interchange may result in insufficient air volume or fan overload. System compatibility needs to be confirmed before replacement.

Misunderstanding 3: Only look at the filtration efficiency and ignore the test particle size. 99.97% of HEPA is against 0.3μm particles, and 99.9995% of ULPA is against 0.12μm particles. The test benchmarks of the two are different, and it is meaningless to directly compare the numbers.

Overview of comparison between HEPA and ULPA

Aili Industrial——Full industry chain filter manufacturer

Aili Industrial has been deeply involved in the field of clean room equipment for nearly two decades. From filter material selection, folding process to frame sealing, it has independently mastered the core manufacturing technology of HEPA high-efficiency filters and ULPA ultra-high-efficiency filters. The products cover H13 and H14 level HEPA filters (filtration efficiency for 0.3μm particles ≥99.97%-99.995%) and U15 and U16 level ULPA filters (for 0.12μm particles). Particle filtration efficiency ≥99.9995%-99.99995%), using imported ultra-fine glass fiber filter paper or PTFE filter membrane. Each unit is scanned and tested for leaks one by one before leaving the factory to ensure 100% standard delivery. Aili Industrial can provide professional filter selection suggestions based on your cleanliness level and process requirements, adapting to the different cleaning needs of 13 major industries such as semiconductors, panel displays, pharmaceuticals, food, and data centers.

If you need HEPA or ULPA filter selection suggestions, please contact the professional technical team of Aili Industry.