Why does the same air volume produce different cleaning and protection effects?
Air volume is a commonly used parameter in clean system comparisons. However, even if the air volume of the two systems is the same, the protection effect may be different. Air volume only indicates the amount of air, not where the air passes, what it covers, or where it brings pollutants.
To judge the protection effect, you need to look at the air supply direction, effective coverage, pollution source location and return air path. The following will start with the airflow path, coverage, location of pollution sources, return air conditions and on-site verification.
The air volume only describes the total volume, not the path.
Air volume is the volume of air passing through the air supply surface per unit time. It reflects the air delivery capacity of the system but not the actual path of the air.
Two options with the same air volume may appear:
The protection effects of the two paths are completely different. The total air volume is the same, but the risk of contamination at the product location can vary significantly. To determine the airflow path, please refer to How will the airflow change when the air supply distance increases?。
The direction of air supply determines where the air passes first
The direction of the air supply affects the order in which the air passes. Ideally, clean air should pass through sensitive products first, then through the source of contamination, and finally out.
If the direction is reversed, the air passes through the source of contamination first, potentially bringing particles to the product location. The air supply direction should be determined based on product location, operating actions and pollution source distribution. For airflow organization considerations, please refer to How to establish a local clean area in an open workstation?。
Effective coverage affects continuity of protection
The air volume is the same, but the effective coverage of the air supply surface may be different. When coverage is insufficient, the product may be in a weak protection zone.
Need to confirm:
Whether key workstations are covered by air supply;
Whether there are gaps or breaks in coverage;
Is the airflow at the product location stable?
Does the wind speed at the edge meet the requirements?
For the relationship between coverage and number of devices, please refer to How does clean air supply coverage affect the number of equipment? , the judgment of the effective air outlet area can be referred to How should we look at the effective air outlet area of FFU?。
The location of pollution sources affects the difficulty of protection
The location of the pollution source determines the difficulty of protection. When the pollution source is located upstream of the product, particles may be carried to the product by the air flow; when it is located downstream, the impact is relatively small.
Should be recorded:
Location of equipment producing dust;
Personnel activity location;
Material unpacking and transfer locations;
Process exhaust and exhaust location.
The location of pollution sources and the direction of air flow should be considered together to avoid pollution sources upstream of the protection path. To distinguish the sources of pollution, please refer to How to distinguish external and internal contamination when particles exceed the standard?。
Return air path affects particle removal
The air volume is the same, but the return air path is different, and the particle removal effect may be different. Poor return air or short-circuited air flow will make the air volume in some areas unable to be effectively utilized.
Need to confirm:
Whether the position of the return air outlet is reasonable;
Whether there is an airflow short circuit;
Whether the return air channel is clear;
Whether the exhaust air and supplementary air are balanced.
To troubleshoot airflow short circuits, please refer to What particle problems can airflow short circuits cause? , for issues regarding the reflow area, please refer to Why is it easy for contamination to accumulate in the return flow area?。
Structural occlusion changes local airflow
Equipment, fixtures, tools and materials may block air supply and alter local airflow. The air volume is the same, but the shielding is different, and the protection effect may be different.
For the problem of dead corners caused by stacking items on the workbench, please refer to Will stacking items on the workbench create a pollution dead zone? . Interference from operating arms, please refer to How will operating the arm interfere with the air supply to the workbench?。
Dynamic conditions affect results more than static conditions
The air volume is the same under static conditions, but the protection effect may be different under dynamic conditions. Human motion, equipment movement, and door opening operations can all change airflow.
Verification should cover actual operating conditions rather than just testing static. To determine the operating status of the equipment during acceptance, please refer to Which equipment should be in operation during acceptance? , the requirements for dynamic verification can be referred to What preparations need to be completed before clean room acceptance?。
On-site verification confirms protection effect
Judging the protection effect ultimately depends on on-site verification. Verification content includes:
Wind speed and airflow direction at key locations;
Airflow coverage of product location;
Particle concentration and recovery time;
Stability under dynamic conditions.
If air volumes are the same but protection is different, airflow paths and coverage should be compared, not just air volume numbers. The problem of average wind speed masking local differences can be referred to Why does the measured average wind speed not mean that the air flow is uniform?。
Project judgment example
In a certain project, two air supply layouts have the same air volume. One directly covers the product, and the other flows through the material box first. The particle results at the workstation are significantly different. Adjustment method: Adjust the air supply direction so that clean air passes through the product first. After adjustment, the protection effect is improved.
The air volume of another project is the same, but the return air channel of one device is blocked and the air flow is short-circuited. Adjustment method: Clean the return air channel and rebalance the air volume. The particles dropped after adjustment.
These two situations illustrate that the same air volume may produce different protective effects, which depend on the airflow path, coverage, location of the pollution source, and return air conditions.
Key points for selection and acceptance inspection
Check items |
Confirm key points |
Air supply direction |
Clean air comes first |
Coverage |
Check for occlusion gaps |
Exit path |
Avoid short-circuit return wind |
dynamic load |
Keep comparison conditions consistent |
Location of pollution source |
avoid being upstream |
Return air conditions |
Confirm there is no short circuit |
Acceptance scope |
Distinguish between air volume and effect |
Aili industrial equipment supporting support
The same air volume does not necessarily bring the same protection effect. The key lies in the airflow path and coverage. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can check the air supply direction, coverage, working points and operating settings based on product location, pollution source distribution and return air conditions, helping to convert air volume into actual protection effects, rather than just comparing air volume numbers.
