How to troubleshoot fluctuations in ULPA particle count results? Sampling location and measurement error

Fluctuations in particle counts associated with ULPA filters should be examined for sampling locations, flow rates, piping, instrumentation, and actual contamination events. Statistical fluctuations at low concentrations also need to be interpreted according to the method, and you cannot just pick the lowest reading. To troubleshoot particle count fluctuations, we must first distinguish between two types of fluctuations: one is the fluctuation of the measurement system, with repeated measurements at the same location and under the same working conditions, the readings themselves have a certain degree of discreteness; the other is the fluctuation of real pollution events, where the particle concentration in the environment is indeed changing. When the two kinds of fluctuations are mixed together, it is easy to regard instrument noise as pollution, and it is also easy to regard real anomalies as accidental fluctuations. Aili Industry isFFU fan filter unit andIn the matching of EFU equipment end fan filter unit , operating status records can be combined to help distinguish measurement fluctuations and actual working condition changes.The FFU computer group control system records particle count, air volume and operating mode by point, and fluctuation analysis has a traceable data basis.

1. Check the measurement chain: check the instrument, sampling volume and pipeline one by one

Check the instrument status, sampling volume, connection leakage and pipeline layout. Changes in pipe length or sampling port should be recorded to avoid introducing new measurement differences.

Any change in any link in the measurement chain will cause the reading to fluctuate. If the sampling flow rate of the particle counter is unstable, the count per unit volume will fluctuate; if the sampling pipeline leaks or is bent, particles may be deposited or lost during the transmission process; if the pipe length or the position of the sampling port is changed, the measurement conditions have changed, and the new and old data cannot be directly connected. Aili Industry isThe HEPA/ULPA filter matching plan explains the sampling conditions of the monitoring points.The FFU computer group control system records instrument status and data refresh. When fluctuations occur, you can first check the instrument and pipeline status to confirm whether the readings are generated under valid conditions. The relationship between levels and filtering requirements can be found inISO cleanliness level comparison。

2. Connect airflow and activity: whether the fluctuations have repeating patterns and spatial correlations

Observe people moving around, equipment starting and stopping, door opening and wind speed changes to confirm whether the fluctuations have repeating patterns and spatial correlations.

Fluctuations caused by real pollution events are often associated with specific activities or conditions: brief increases in counts when people pass by, spikes when equipment starts and stops, readings change within minutes after a door is opened. If the fluctuations are irregular, all points appear at the same time, and do not match any activity, it is more likely to be random fluctuations of the measurement system. Aili Industry isEFU equipment end fan filter unit, the air flow change nodes can be confirmed according to the equipment action sequence.In the The FFU computer group control system records particle counts, access control signals and equipment operating status, which can be compared in time series during fluctuation analysis. For the correspondence between monitoring data and process events, please refer toHEPA FAQs and Selection Guide。

3. Statistical fluctuations at low concentrations: Reading fluctuations are not equal to pollution changes

In low-concentration environments, the statistical dispersion of particle counting itself will account for a larger proportion. When the sample volume is small, the inclusion or omission of individual particles can cause a significant percentage change in the count, but this change may not be statistically significant.

To determine whether the fluctuation is significant, the sampling volume and counting level should be combined and interpreted according to the statistical rules specified in the method, rather than based on the numerical difference between the two readings. Aili Industry isULPA ultra-high efficiency filter, the data interpretation method is explained according to the project sampling conditions.In the monitoring plan related to The sampling parameters and data recorded by the FFU computer group control system can be statistically analyzed according to rules to avoid misjudgment of statistical fluctuations as pollution events. For data interpretation methods, please refer toULPA ultra-high efficiency filter FAQ and selection guide。

4. Form conclusions according to established procedures: Do not repeatedly change measuring points until the values ​​become lower.

The prescribed sampling time, measuring points and result processing methods shall be adopted, and evidence shall be retained for abnormalities. Repeatedly changing the measuring points until the value is low is not an effective troubleshooting.

The purpose of fluctuation troubleshooting is to find the cause, not to make the data look qualified. If the location of measuring points, sampling time or processing methods are repeatedly adjusted during the investigation process, the data will be different after each adjustment, and the final set of data to be retained becomes a subjective choice. Aili Industry isThe non-standard ULPA filter project monitoring plan is implemented according to the confirmed measuring points and sampling procedures.The FFU computer group control system records the measurement point number and sampling parameters. Each measurement during the investigation process has a corresponding record, and the conclusion corresponds to the final confirmed test conditions. For programmatic management of device-side monitoring data, please refer toEFU FAQ and technical support。

5. Related questions and answers

Can occasionally a high value be deleted directly?
It should be identified and dealt with according to procedures, and should not be eliminated just because it does not meet expectations.

Are large fluctuations necessarily due to changes in pollution sources?
uncertain. Instrument status, sampling conditions, and statistical fluctuations at low concentrations may cause reading changes and should be investigated one by one.

Is it okay to test repeatedly until the value is low?
Not recommended. It should be carried out in accordance with the prescribed procedures and measuring points, and evidence should be retained for exceptions. Data cannot be selected by changing measuring points.

6. Related articles

ULPA ultra-high efficiency filter FAQ and selection guide

FFU computer group control system

EFU FAQ and technical support

HEPA FAQs and Selection Guide

7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isFFU fan filter unit andIn the matching of the EFU equipment end fan filter unit , operating status records are combined to help distinguish measurement fluctuations and actual working condition changes.The FFU computer group control system records particle count, air volume and operating mode by point, records instrument status and data refresh status, and has a traceable data basis for fluctuation analysis.HEPA/ULPA filter matching plan explains the sampling conditions of monitoring points.The monitoring plan related to ULPA ultra-high efficiency filter explains the data interpretation method according to the project sampling conditions;The EFU equipment-end fan filter unit can confirm the airflow change nodes according to the equipment action sequence.The non-standard ULPA filter project monitoring plan is implemented according to the confirmed measuring points and sampling procedures.The FFU computer group control system records the measuring point number and sampling parameters. 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.