How do the resistances of HEPA, glass fiber ULPA and PTFE ULPA compare?

This question often comes up in selection or replacement discussions. Someone took a piece of information saying that the resistance of ULPA of PTFE is lower than that of HEPA of glass fiber, and wanted to judge which solution is more energy-saving based on this. Some people also see that ULPA of the same size has higher resistance than HEPA, and they believe that 'the higher the grade, the greater the resistance.'

Both judgments are problematic. Comparison of resistances, provided the conditions are aligned. The conditions are not aligned, and it makes no sense to put the data together.

What columns should be in the comparison table?

First, clearly state the object of comparison.

grade. Is it H14 or U15? Is it fiberglass or PTFE? The grade and filter material must be marked.

Frame size and depth. The length, width and thickness must be consistent, otherwise the relationship between air volume and resistance will change.

Effective filter area. This is the most easily overlooked item. For products of the same size, the effective area may vary significantly by adjusting the pleat density or structural form. For products with a large area, the passing wind speed of the filter material is lower under the same air volume, and the resistance may naturally be smaller.

Test air volume. What is the air volume corresponding to the resistance data? Readings at different air volumes cannot be directly compared.

Test basis. Is the report tested on filter material samples or finished products? What are the test methods and conditions?

Once these are listed together, there will be a basis for comparison. Just listing a 'resistance value' cannot explain which solution is more suitable.

Medium and structure jointly influence results

The resistance characteristics of PTFE and fiberglass do differ, but this difference is not the only variable.

Glass fiber filter material : The structure is relatively stable and the performance is relatively consistent under normal working conditions. Specific resistance depends on fiber diameter, grammage and pleat design.

PTFE filter media : Membrane structures may have different airflow channel characteristics. In some designs, PTFE may achieve lower resistance, but this depends on the specific product design and is not a property inherent in the material name.

Structural design may have a greater impact than materials. Also using PTFE, if one product has a large effective area and reasonable pleat pitch design, the resistance may be low; while another product may have a small area or too dense pleat pitch, and the resistance may be high. The shape of the protective net, edge sealing and channel will also affect the resistance of the whole machine.

Therefore, you cannot judge the level of resistance just by the words 'PTFE' or 'glass fiber'. It depends on the complete curve and structural data of the specific product. For discussions on filter material selection, please refer to the instructions related to glass fiber and PTFE. For HEPA and ULPA product types, please refer to the instructions respectively. HEPA high efficiency filter and Information on ULPA ultra-high efficiency filters .

Make decisions based on actual working conditions

After obtaining comparable data, the judgment sequence is as follows.

Compare the design air volume. How much air volume is required for the project? At this air volume, what is the resistance of each candidate product? This is the most direct point of comparison.

Check the final resistance conditions. When the filter element reaches the advanced stage of dust accumulation, the resistance will rise. It is necessary to confirm how much margin the fan has under the final resistance. If you only select based on the initial resistance, the air volume may be insufficient later. For specific calculation methods, please refer to the relevant instructions on initial resistance and final resistance.

Evaluate operational energy consumption. For products with low resistance, the static pressure required by the fan may be smaller under the same air volume, and the energy consumption in long-term operation may also be lower. But this account must be calculated based on the fan efficiency and control method, not just the resistance number.

Consider maintenance costs. Products with a large effective area may have higher dust holding capacity and longer replacement cycles. This part of the cost difference is sometimes more worthy of attention than the purchase price difference.

Lower initial resistance alone does not prove longer life or better integrity. Resistance and integrity are two dimensions, verified separately. Supporting FFU fan filter unit or fan filter unit at the EFU equipment end , the operating point of the unit and the resistance of the filter element must also be checked. For the filter element used in the

Project judgment example

Two samples are marked with resistance data: one is fiberglass U15 and the other is PTFE U15. The former has higher resistance than the latter.

Seeing this data, we cannot directly say 'PTFE's ULPA resistance is lower'. It is necessary to confirm first: whether the test air volume of the two products is the same, whether the effective area is consistent, and whether the test object is the filter material or the finished product.

If conditions are different, the difference in resistance may come from the structure or testing conditions rather than the material itself. After the conditions are aligned, the actual air volume, available static pressure and maintenance requirements of the project will be combined to determine which solution is more suitable. involving HEPA/ULPA air filter products of different grades are compared in the same way.

Selection and Acceptance Checklist

About Aili Industrial’s resistance accounting cooperation

When it comes to resistance comparison, the clearer the data conditions, the more evidence-based the judgment will be.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide HEPA/ULPA products of different grades and filter materials. The resistance curve and test conditions of the corresponding model can be provided according to project requirements. The filter and When the FFU fan filter unit and EFU are matched, the filter element resistance and fan operating point can be calculated together during the planning stage to facilitate comparison of the applicability of different solutions.

Providing design air volume, available static pressure, installation space and comparative dimensions during inquiry will help obtain comparable data. Specific performance is subject to the testing data of the corresponding model.