Today's advanced particle measuringsystems and particle counters are used inmultiple cleanroom industries around theworld. The data recorded and used wheneither certifying a cleanroom, a clean airdevice or for in-process monitoring isdeemed critical information.

Decisions regarding this data are madeon an operational level. For example, inthe semiconductor industry, product yieldsand product quality decisions are madewith this information. In the

pharmaceutical industry, batches arereleased into the market based on thecritical particle count data. This articlereviews the best housekeeping methodsthat users of particle counters can applyto help mitigate against loss of dataintegrity and accuracy.

Numerous events can affect the dataintegrity and accuracy of an instrumentset up for particle detection. Cleanroomoperators and personnel interacting withthe device should consider the following

conditions when using and managing aparticle counter:

� Transportation while in use� Capping the sample inlet in between uses� Instrument cleaning (housing)� Sensor cleaning (zero filter)� Environmental decontamination� Sample tube length� Maintaining calibration intervals� Shipping back for service

18 March 2019

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Jason Kelly, VP of Services, Lighthouse Worldwide Solutions, reveals the best housekeeping methodsthat users of particle counters can apply to help mitigate against loss of data integrity and accuracy

PARTICLE COUNTER MANAGEMENT FORBETTER DATA INTEGRITY AND RELIABILITY

March 2019 19MONITORING

sensor can adversely impact sensorperformance as well as the results.

Instrument cleaning When cleaning the external enclosure ofthe particle counter the instructions in theuser manual should be followed. Here, therecommendation is to use the approvedcleaning agents and to lightly wipe downthe external enclosure.

Some particle counters have excellentwipe downable brackets and enclosuresthat hide cabling and vacuum tubing. Forremote particle counters, it is advisable tomount the instruments in such cleanroomfriendly enclosures.

Sensor cleaningIt should come as no surprise that aparticle counter’s internal sensor canbecome contaminated with unwantedspecks of dust or other matter. Forexample, if the instrument was previouslyused in a dirtier environment and taken toa cleaner environment then a sensor purgewould be required.

By cleaning the sensor, users caneliminate cross-contamination risks. Italso prevents re-aspirated particles in thebottom of the sensor from being stirred upand recounted again.

A purge time before sampling isrecommended to allow the particlecounter to clean up. Moreover, using azero count filter helps the sensor “zero”out and provide verification ofcleanliness. A zero count filter is also agood troubleshooting tool to verifysensor cleanliness.

Environmental decontamination One of the biggest issues facing dataaccuracy is the problem aroundenvironmental cleaning solutions, such as sprays finding their way into anuncapped sensor.

Cleaning solutions droplets may depositon the optics and mirrors, which results inclouding of the optics and mirrors. Thisclouding effect can have a major impactwhen the calibration of the unit fails.

If the unit is in for an annualcalibration, then the failure impact couldbe as large as 12 months. Depending onthe level of “as found” failure, the datafrom the particle counter could beconsidered void for 12 months. That’s alot of records where product releasesassociated with the particle counter’s datais questionable. Such an impact couldinfluence a product recall.

With this in mind, when cleaning yourcleanroom environment always make sureyour particle counter inlet cap is on. Avoid

any liquid droplets or cleaning solution toenter the particle counter sensor.

Seek out suppliers of particle counterswith self-diagnostics built into the sensor.These smart sensors can raise a servicealarm if the sensor becomes contaminatedso you can pull the unit from productionin real time and investigate the issuestraight away, avoiding the pain of a failed“as found” calibration.

Sample tube lengthIt has been well documented that particlelosses are an issue with larger particles,above 5.0 μm. The reason is simple: longsample tubing lengths and bends causelarger particles to become trapped insidethe tubing. Consequently, it is advisable tokeep sample tubing to a minimum to avoidsuch losses.

Moreover, as these trapped particles canbe accidentally introduced into the sensorand be falsely counted, it is best to keep thesample tubing to a minimum.

Transportation while in useParticle counters are sensitive measuringdevices, which have been designed to uselasers and photo-optics to collect particlesize and quantity data. They may have arobust housing, but these are delicateinstruments, hence they should behandled with care. The advice is to avoidany shock or major vibration that maymisalign the laser and optics.

Some facilities use cleanroom-friendlycarts and others carry the units by hand.While not in use, it is recommended thatthe particle counter is stored in a securebox or location.

Capping the sample inlet between usesIt is extremely important to keep thesample inlet capped at all times when theparticle counter is not in use. Any debrisor large contamination getting inside the

Particle counter mirror contaminated fromcleaning process

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The last thing a company needs is afailed “as found” calibration. This createsa major quality issue that can result insignificant disruption and adverselyimpact product quality when bad data is recorded.

Manufacturers recommend at least anannual calibration. However, users ofcontinuous particle measuring systemsand monitoring systems should considermore frequent assessment to ensureconfidence between service.

Shipping back for serviceAs mentioned earlier, particle countersare sensitive measuring devices.Therefore, when units are shipped backto the manufacturer for service, it iscritical that instruments are properlyinsulated and packed. Manufacturersoffer shipping cases and even the original

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The Pharmaceutical Inspection Co-operation Scheme (PIC/S) describes inAnnex 1 of the GMP guide for themanufacture of sterile medicinal products,the need to minimise particle countertubing lengths.

Paragraph 6 of the section entitledCleanroom and Clean Air DeviceClassification states: “Portable particlecounters with a short length of tubingshould be used for classification purposesbecause of the relatively higher rate ofprecipitation of particles >/5.0μm inremote sampling systems with longlengths of tubing."

Furthermore, paragraph 11 of thesection entitled Cleanroom and Clean AirDevice Monitoring, reads: “Airborneparticle monitoring systems may consistof independent particle counters: anetwork of sequentially accessedsampling points connected by manifold toa single particle counter; or acombination of the two. The systemselected must be appropriate for theparticle size considered.”

The document continued: "Whereremote sampling systems are used, thelength of tubing and the radii of anybends in the tubing must be considered inthe context of particle losses in the tubing. The selection of themonitoring system should take account ofany risk presented by the materials usedin the manufacturing operation, forexample, those involving live organisms or radiopharmaceuticals."

Maintaining calibration intervalsIt is crucial, and a regulatory requirement,that critical monitoring and measurementinstruments are calibrated annually.

cardboard shipping box and foam insertsshould be utilised for return shipping.Always ensure the unit is powered off, thebattery is removed and the inlet cap isfitted securely.

Key considerationsParticle counters are sensitiveinstruments used in many applicationswhere the data they collect is deemedprocess critical. Whether for cleanroomclassification or routine processmonitoring, the way a particle counter ishandled, operated and transported makesa big difference in maintaining the datafrom the instrument.

With more and more companies beingcited for data integrity issues, it isimportant to understand the proper way to use and manage a particle counter.

Equally, with increasing emphasis ondata integrity, newer particle countersfeaturing built-in self-diagnostics arebecoming available on the market.

This new “self-diagnostic” technologycan identify sensor contamination issuesin real-time so that users are alerted toinstances where contamination can lead tobad data and ultimately failed calibrations.

Choosing such technology ensures usersare notified when events occur so they cantake immediate action to safeguard theirproducts and customers.

If you follow the advice outlined in thisarticle and implement theserecommendations into SOP’s, then youare well on the way to securing your dataand understanding best practices whenusing particle counters.www.golighthouse.com

The bibliography of this article is available atcleanroomtechnology.com

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Particle counter in LAFcabinet with short length ofsample tubing. Sampling in

the work zone

Particle counter insideshipping box with insulationfoam inserts for safe shipping

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