How does a change in working height affect the detection position?

The sampling height of the clean area is usually determined based on the actual exposure position of the product. If the working altitude changes, the original sampling location may no longer represent the new protective surface. The particle concentration and airflow conditions on the floor, countertop, and upper space of the equipment may be different, and the test results at the original height cannot be directly applied to the new working conditions.

Changes in working height are not just changes in height values, but may also be accompanied by changes in structures, occlusions and airflow paths. The following will start with the definition of sampling height, air flow conditions, structural changes, and verification methods.

The sampling height should correspond to the actual working surface

The height of the sampling location should be chosen at the height where the product or operation actually occurs. Common work surfaces include:

• Ground or low operating surface;

• Countertop or workbench height;

• A specific height within the equipment cavity;

• The operating height corresponding to the standing or sitting posture of the person.

If the product is handled on a countertop, the sampling point should be at countertop level; if the product is exposed at a specific height inside the equipment, the sampling point should be close to that location. The sampling height does not correspond to the actual working surface, and the measured results may be higher or lower. For the selection principles of sampling point locations, please refer to Why can’t the sampling point be located just below the air supply outlet?。

Different airflow conditions at different heights

Airflow conditions may be different at different heights in the same area. After the supply air blows out from the air outlet surface, the speed and direction will change with the distance. The wind speed is higher near the air outlet surface, and the wind speed may be lower at locations far away from the air outlet surface, and the airflow direction may also change.

For a workbench with vertical air supply, the airflow conditions at the top and near the table are different; for a workbench with horizontal air supply, the airflow conditions at the rear and front are also different. The sampling height should be determined based on the actual air flow status, and one height cannot be used uniformly. The influence of air supply distance on air flow can be referred to How will the airflow change when the air supply distance increases?。

Working height changes may be accompanied by structural changes

When the working height changes, it is often accompanied by adjustments to the table, fixtures or support structures. These changes may alter airflow paths:

• Raising the countertop may block the lower air supply;

• Elevated fixtures may create shadows under the air supply surface;

• Changing the position of the workpiece may place it in a different airflow zone.

When determining the sampling location, the impact of structural changes on airflow should also be confirmed. For the problem of airflow dead spots caused by stacking items on the workbench, please refer to Will stacking items on the workbench create a pollution dead zone?。

Verification points after altitude changes

After the working height changes, you should reconfirm:

• New work surface heights and sampling locations;

• Wind speed and airflow direction at that altitude;

• Whether the product exposure location is within the effective protection range;

• Whether structural changes affect airflow paths;

• Whether the protection is stable under dynamic conditions.

Verification should be carried out under actual operating conditions, covering representative operating actions. If you only judge based on the original height data, you may miss the weak locations under the new working conditions.

Special Considerations for Lift Stations and Adjustable Table Tops

The working height of the lifting station and adjustable table will change with the operation. The sampling position of this type of workstation needs to consider the protection conditions at different heights.

Should confirm:

• which heights are common working positions;

• Whether the airflow can cover the product at different heights;

• Whether height adjustment affects the air supply path;

• Check whether the adjustment mechanism itself produces dust or blocks airflow.

If the equipment supports height adjustment, it should be confirmed separately at common working heights instead of just measuring a fixed position.

Differences between floors, countertops and equipment upper levels

Grain conditions may differ at different altitudes. The area near the ground may be affected by the movement of people and material handling; the height of the table is the main operating area; the space above the equipment may be affected by thermal plumes and structures.

The sampling location should be determined based on the actual exposure layer of the product. If the product is inside the equipment, the sampling point should be close to the internal working surface of the equipment, rather than only measuring the external space of the equipment. For sampling location planning of closed equipment cavity, please refer to How to plan clean air supply for closed equipment cavities?。

Record sampling height and adjustment conditions

Sampling records should include height information and conditions for working height adjustments. include:

• The actual height of the sampling probe;

• The height and condition of the working surface;

• Whether it is in the adjusted working position;

• Structural changes and operational settings.

These records help to subsequently determine the working conditions corresponding to the data. If the height of subsequent work changes again, it can be reconfirmed against the records.

Equipment selection and terminal matching

For the equipment and filtering configuration involved in sampling, please refer to FFU clean air supply products and EFU equipment side fan filter unit . Filter installation, sealing and leak detection requirements can be learned HEPA and ULPA filters . 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?。

Project judgment example

A certain workstation was changed from a low table to a higher assembly rack, but the original sampling height was still near the table. The test data is qualified, but the upper workpiece particles are too high. The investigation found that the height of the new working surface was not within the original sampling range, and the airflow conditions at this height were different. Adjustment method: Re-distribute points according to the new height of the working surface to confirm the protection effect of the upper position. The particles dropped after adjustment.

Another project used a lift station and was tested at only one height. In actual use, product protection conditions are different at different heights. Adjustment method: Confirm separately at common working heights, and record the airflow and particle status at each height. After adjustment, the protection range of the workstation is clear.

These two situations illustrate that after the working height changes, the sampling position should be rechecked to confirm whether the new working surface is within the effective protection range.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Changes in working altitude can alter the effectiveness of sampling locations and may also alter airflow conditions. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can check air supply coverage, sampling locations and operating settings based on the project's working height, structural changes and airflow organization requirements to help determine whether the new working surface is within the effective protection range, instead of using the original data. Specific models can be viewed FFU clean air supply products , supporting equipment can be viewed EFU equipment end fan filter unit , please refer to the filter package. HEPA and ULPA filters。