What is the difference between cleanliness level and filtration efficiency?

In clean room project communication, these two words are often said together, and sometimes they replace each other. For example, 'After using H14, the room is rated at level 100', or 'The room does not reach ISO 5, is the filter efficiency insufficient?'

Neither statement is accurate. Cleanliness level and filtration efficiency are evaluated by two things. One is based on the air condition in the space, and the other is based on the performance of the product itself. Related, but not directly convertible. If you can't distinguish between these two things, your selection will go astray, and your investigation will not be able to find the right direction.

Filtration efficiency is a component performance indicator

Filtration efficiency describes the filter's ability to capture particles of a specific size under specified test conditions.

This data comes from laboratory or factory testing. The test standard, test air volume, test particle size and overall or partial efficiency will be noted on the report. For example, levels such as H13, H14, and U15 are all measured under corresponding standards.

The key point is: it is a product indicator, not a space indicator. The report is qualified, indicating that the filter meets the requirements under the test conditions. However, after it is installed on site, the actual collection effect is also affected by the installation seal, air volume and air flow organization. If there is a problem in these links, no matter how good the filter itself is, it will not be able to play its due role.

Cleanliness level is an indicator of space status

Cleanliness levels describe the concentration of particles in the air in a given area.

It needs to be tested on site, in accordance with the methods, particle sizes, sampling points and operating conditions specified in the standard. The test results reflect the actual state of the space at that time, not the performance of a certain device.

There are many sources of on-site particles: movement of people, unpacking of materials, movement of equipment, opening of doors, and introduction of return air. These factors add up to form the final concentration. Even if the filter efficiency is very high, if the room air volume is insufficient, the air flow is short-circuited, or the pollution source is continuously released, the rating may still not meet the standards.

There are system conditions between the two

From filtration efficiency to cleanliness level, there are several links in between. Only by clarifying this link can we start with selection and troubleshooting.

Installation seal : Whether the interface between the filter and the installation frame is reliable. Frame bypass allows unfiltered air to flow around the filter media and directly into the clean side. In many on-site non-compliance cases, the problem lies here, not the efficiency of the filter element.

Air volume matching : Whether the actual air volume passing through the filter is within the design range. Insufficient air volume will reduce particle dilution and removal capabilities; too high air volume may increase disturbance and energy consumption. Both will affect the final outcome.

Air flow organization : Whether the air supply surface coverage is complete, whether the return air path is smooth, and whether there are eddies and short circuits. No matter how efficient the filter is, it will not be effective if the airflow does not pass through the protected area.

Pollution load : The amount of particles released by personnel, equipment and processes. If the source of pollution persists, improving filter efficiency can only improve part of the problem, but cannot solve the entire problem.

If any of these four levels of conditions is not handled well, the investment in filtration efficiency will be compromised.

The acceptance data should be separated

During project acceptance, the data on these two types of indicators must be recorded separately and cannot replace each other.

Filter side: efficiency level, applicable standards, test air volume, test report and unit-by-unit number. These are product data.

Installation side: On-site leak detection records, covering filter material surface, edge sealing and installation interface. These are sealed status data.

Space side: Clean area particle test report, including measurement point distribution, sampling method, operating status and test results. These are space status data.

Each of the three types of information answers a question: whether the product is qualified, whether the installation is sealed, and whether the space is up to standard. Mixed into one document, the boundaries of responsibility are unclear when something goes wrong.

Aili Industrial has manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing. When doing a clean level project, product parameters, installation interfaces and on-site verification requirements can be checked under the same project conditions to make the connection between filtration efficiency and space objectives more reliable. Related products can be viewed FFU clean air supply products and HEPA and ULPA filters , equipment-side applications can be referred to EFU equipment side fan filter unit。

On-site judgment example

When the particle test in a certain project's room failed to meet standards, the first reaction was to replace it with a higher-grade filter.

After investigation, it was found that the efficiency report of the filter itself was qualified, but a sealing gasket in the installation frame was displaced, forming a partial bypass. Unfiltered air enters the clean side from here. Even if the filter element is replaced with a higher grade filter element, the bypass path still exists. The treatment direction is to repair the seal, not to upgrade the filter element.

Another project room met the standard, but the particle concentration increased after a period of use. The inspection found that dust accumulation in the filter element caused the air volume to decrease and the air flow organization was also affected. This situation requires maintenance or replacement of the filter element rather than adjusting the filter rating.

What both cases have in common is this: the problem lies with the on-site system, not the efficiency number of the filter.

Key points for selection and acceptance inspection