How to choose between H13, H14 and U15?

H13, H14 and U15 are often compared together. Many projects will directly ask: Is U15 definitely better than H14? Can H13 satisfy a certain clean area? These questions cannot be answered by level names alone. These three levels describe the efficiency requirements of the filter under specified test conditions, and are not the corresponding labels for the ISO level of the room. When choosing, you should look at the filter classification standards used, process-sensitive particle size, complete machine air volume static pressure, installation sealing and leak detection conditions.

If you only choose based on 'the higher the level, the better', two problems may occur: the areas that should be upgraded are not upgraded, or the entire site uses U15. As a result, the fan cannot be driven, the resistance is too high, and the operating cost increases. The following will start from the testing caliber, complete machine matching, sealing and leak detection, and operation and maintenance.

First unify the test caliber of the filter

When comparing H13, H14 and U15, the first step is to confirm the filter classification standard used. Different standards may have different definitions of efficiency, test particle sizes, and test methods. When checking the report, you should pay attention to:

• Standard system adopted;

• Test whether the particle size is the easiest to penetrate or a fixed particle size;

• Test whether the air volume is consistent with the actual air volume;

• Is the reporting object a filter material sample or a complete filter?

• Overall efficiency or local efficiency.

If you are still unclear about these calibers, you can read How to read the test particle size in the filter efficiency report? , first distinguish the difference between fixed particle size and MPPS. The percentages under different diameters cannot be sorted directly, nor can the filter material sample data be regarded as the result of the finished filter.

H13, H14 and U15 describe efficiency requirements

These three grades describe the efficiency requirements of the filter under specified test conditions. Differences in grade do not represent room grade differences, nor do they represent differences in on-site particle concentration. The cleanliness level of a room or area must be comprehensively judged based on air supply volume, airflow organization, sealing, pollution load and operating status.

If you are still unclear about the difference between space rating and filter efficiency, you can read What is the difference between cleanliness level and filtration efficiency ? Avoid taking the filter level directly as the room level. The cleanliness level must also indicate the measured particle size. For details, please refer to Why must the particle size be indicated in the cleanliness grade?。

Deducing filtration requirements from process particle targets

Before choosing a level, confirm three things:

• Sensitive particle size : which particle size the product is most sensitive to;

• Background loading : Concentration and sources of particles in the air upstream of the filter;

• Allowable Level : The level of particles allowed on a product surface or critical area.

If the process is particularly sensitive to tiny particles, it may be necessary to add control indicators and detection capabilities, and then compare H14 and U15. If the background load is low and the product-sensitive particle size is large, a suitable H13 solution may also meet the requirements. For specific judgment, please refer to How do HEPA and ULPA match cleanliness goals? , first confirm the filtering requirements, and then fall to the specific level.

When it comes to protecting the interior of the device, there is also a combination of cavity airflow paths and exposure times. Can be referenced How to plan clean air supply for closed equipment cavities? , first confirm the protection boundary, and then determine the filtering level.

After determining the level, check the working point of the whole machine

Higher efficiency filters tend to have higher resistance. After switching to U15, if the fan operating point remains unchanged, the actual air volume may decrease, resulting in insufficient terminal wind speed or insufficient air changes.

When selecting, you should check:

• The initial resistance and final resistance of the filter at the target air volume;

• The working point of the fan under corresponding resistance;

• Whether the input power and noise of the whole machine are still within the allowable range;

• Whether the installation space accommodates thicker or denser filters.

If the filter area is insufficient, the fan may require higher pressure to maintain flow. For details, please refer to How does insufficient filter area affect fan selection? . If the wind speed facing the filter is too high, it may also increase resistance, power consumption and noise. Please refer to What will be the impact if the wind speed facing the filter is too high?。

Please refer to the reading method of working point Why should we look at the complete performance curve when selecting FFU? , and confirm the test configuration corresponding to the nominal air volume, please refer to Is FFU's nominal air volume tested with a filter?。

The rated air volume must match the actual operating air volume

The rated air volume of the filter is used to describe its specified test or design conditions. The actual operating air volume should fall within the usage range confirmed by the manufacturer. When selecting a model, you need to check the efficiency, resistance, and fan operating point. You cannot determine replacement based on the same size.

For specific judgment, please refer to How does the filter's rated air volume match the actual operating air volume? . If the air volume drops after replacing the filter, you should first check the operating point instead of directly increasing the rotation speed.

Sealing and installation leak detection cannot be omitted

If the high-efficiency filter is not properly installed and sealed, bypass leakage will allow unfiltered air to enter the clean side. At this time, upgrading U15 cannot achieve the expected results. After installation, the frame seal, installation interface and leak detection conditions should be checked.

If there are abnormal particles on site but the filter efficiency is acceptable, priority should be given to checking the sealed bypass and airflow short circuit. Can be referenced Does higher filtration efficiency necessarily lead to improved site ratings? and What particle problems can airflow short circuits cause?。

Initial resistance and final resistance are used for different judgments

The initial resistance usually describes the pressure drop of a new filter under a specified air volume, and the final resistance is used to judge maintenance or replacement during the agreed use period. The final resistance is not the only life criterion. Damage, moisture, process risks and actual air supply capacity must also be considered.

For specific judgment, please refer to What are the initial resistance and final resistance used to judge? . If the operating pressure differential is abnormally low, a breakage or bypass should be investigated rather than a performance improvement.

No need to upgrade the whole room at the same time

Local areas of key equipment and room background areas may use different filtering configurations, and the working conditions should be evaluated separately. It is not necessary to upgrade U15 in the entire room because of high local requirements.

For example, ISO 5 is written in the ordinary background area and inside the precision equipment, but the process-sensitive particle sizes are different, and the filter selection may be different, and the technical conditions should be formed separately. Whether ISO Level 5 projects must adopt ULPA, please refer to Is ULPA mandatory for ISO Level 5 projects? . For the filtration configuration of open work stations or local protected areas, please refer to How to establish a local clean area in an open workstation?。

Equipment selection and terminal matching

Filter selection should correspond to target particle size and actual resistance.The HEPA and ULPA filter pages have parameters for different levels of products. When selecting, check the efficiency of the specific model at the target air volume.

Please refer to the room background air supply FFU clean air supply products , please refer to the local protection of the equipment side. EFU equipment side fan filter unit . The logic of division of labor between the two lies in The division of labor between device-side EFU and room FFU is explained in detail.

If multiple devices require partition duty and troubleshooting, they can be combined FFU group control system provides unified management.

Project judgment example

The original equipment of a certain project uses H14, and the user proposed to upgrade all equipment to U15. After checking, it was found that the background load in some areas was not high, and the sensitive particle size of the product did not reach the level requiring U15; however, higher filtration configuration was indeed required inside key equipment. Adjustment method: Use U15 in key areas and check the fan working point, and retain H14 in the background area. After adjustment, the system resistance is controllable and the key areas meet the requirements.

Another project directly replaced the U15 filter without checking the fan capacity. After installation, the terminal wind speed dropped. Adjustment method: Check the working point under the initial resistance of the new filter, adjust the fan speed and confirm that the power and noise are within the allowable range. After adjustment, the air volume and filtration efficiency are both satisfied.

These two situations illustrate that the selection of H13, H14 and U15 must be comprehensively judged based on process objectives, background load, system resistance and installation conditions, and cannot be specified solely by grade names or industry habits.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

The choice between H13, H14 and U15 will ultimately come down to the working point of the entire machine. Aili Industrial also does air filters, fans, motors, control systems and complete machine assembly. It can list and compare the resistance, efficiency, installation interface and power changes of different levels of filters under the same target air volume, helping the project determine whether there is room for the fan after upgrading to the first level, whether the sealing method matches, and how much the operating cost will increase. Specific filter parameters can be viewed HEPA and ULPA filters , the complete machine package can be viewed FFU clean air supply products and EFU equipment side fan filter unit。