What should I do if the background particles in ULPA leak detection are too high? Blank testing and background control

of ULPA filter leakage detection are relatively high, the cleanliness status of the instrument, sampling pipeline, environmental interference and method applicability should be checked. When the background particles Inadequate background control may affect the identification of low concentration results. When the background is high, it is difficult to determine whether the signal appearing in the scan is a filter element leak or background noise - the background itself is fluctuating, and signals near the threshold lose their distinguishing meaning. Aili Industry isIn the ULPA ultra-high-efficiency filter testing process, background confirmation is a required step before the test begins: the blank count, pipeline status, and sampling environment are confirmed one by one before the official scan begins, so that the background and signal are separated before the test.

1. Distinguish the background source: instrument, pipeline, environment or aerosol escape

Carry out blank or zero count verification under specified conditions, check pipeline residues, joint contamination and nearby personnel activities to avoid misjudgment of instrument contamination as filter element leakage.

The sources of background particles are usually concentrated in several locations: contamination of the optical cavity inside the instrument, particles attached to the inner wall of the sampling hose, human activities near the sampling port, or upstream aerosol escape. Different sources have different processing methods, and it is more effective to eliminate them one by one than to replace the entire instrument. Aili Industry isThe HEPA/ULPA filter testing process has daily verification requirements for the status of the sampling pipeline and instrument. Before testing, confirm that the background of the instrument is within the allowable range before entering the formal test. The relationship between levels and filtering requirements can be found inISO cleanliness level comparison。

2. Confirm the test environment and stability: a stable background is more important than a low background

Check for nearby operations, upstream aerosol escape and sampling port interference, and then test according to the program control. It is not appropriate to arbitrarily deduct a background value.

The background value itself is not the only problem, the stability of the background is equally critical. When the background is low but the fluctuation is large, the reliability of the scanning signal is still insufficient. Aili Industry isDuring the ULPA ultra-high efficiency filter testing, the background is required to remain stable between multiple samplings before formal scanning begins. The stability record of the testing environment is archived together with the testing data. When inspecting the project on site, you can follow the same idea: do a few blank counts first, and then scan after confirming that the values ​​are stable. For the relationship between leak detection methods and background, please refer toHEPA FAQs and Selection Guide。

3. Record corrections and limitations: Leave evidence behind after dealing with underlying issues

Save verification results, processing actions and retest conditions. If the method cannot meet the judgment ability in this context, the plan should be explained and adjusted.

After processing the high background, it is necessary to record the source, how it was processed, and the level to which the background dropped after processing. These records are the basis for subsequent judgments on the credibility of test results. Aili Industry isDuring the non-standard ULPA filter project testing, the background verification, processing actions and retest conditions are archived with the test report. The project party can compare and confirm that the test conditions are valid during acceptance. If the background cannot be reduced to the level required by the method, the detection limitations should be explained and the plan adjusted instead of processing the data. For the relationship between sealing and leak detection, please refer toULPA ultra-high efficiency filter FAQ and selection guide。

4. The background dropped significantly after replacing the sampling tube. Record the pipeline status.

After replacing the sampling tube, the background dropped significantly. The pipeline status and cleaning process should be recorded to avoid subsequent use of contaminated tubes. Sampling pipeline contamination is an easily overlooked source of background—particles on the inner wall of the hose will fall off and enter the sampling airflow when the airflow passes by, causing the background to be falsely high, but no abnormality can be seen in the appearance.

Aili Industry has record requirements for the replacement and cleaning of sampling pipelines during the testing process.the FFU fan filter unit also has standards for detecting pipeline status. This management method can be converted into pipeline management requirements for on-site inspection. The factory test of For the coordination of background and environmental conditions, please refer toFFU FAQ and technical support。

5. Related questions and answers

Can the background be subtracted directly from the result?
The provisions of the method used should be followed and no deductions should be made to arrive at a qualified conclusion.

Is the high background necessarily an instrument problem?
uncertain. Pipeline residues, sampling port interference, and upstream aerosol escape may cause the background to be high, and should be investigated one by one.

Can I test directly if the background value is low?
Background stability should also be confirmed. When the background fluctuation is large, even if the value is not high, the credibility of the scan results will be affected.

6. Related articles

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7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isIn the ULPA ultra-high-efficiency filter testing process, background confirmation is a required step before the test begins. The blank count, pipeline status, and sampling environment are confirmed one by one before the formal scan begins. The background stability record is archived with the test data;HEPA/ULPA filter testing requires daily verification of the status of sampling pipelines and instruments.the non-standard ULPA filter project testing are archived with the report.The background verification, processing actions and retest conditions during the FFU fan filter unit has specifications for detecting pipeline status, which can be converted into pipeline management requirements for on-site inspection. The factory test of Provide process objectives, installation drawings, operating conditions and acceptance requirements, and can further communicate ULPA standard specifications, non-standard interfaces, samples and batch matching. The specific parameters and test range are based on the confirmed model and technical documents.