Knowledge Centre

Our subject matter knowledge, based on years of industry experience in contamination control, is a valuable FMS asset. And we like to share it. Here’s where you’ll find answers to some of the questions we are frequently asked, along with reference materials and advice on a range of important matters. We update this page with new resources regularly, so keep an eye on it.

If the information below doesn’t solve your particular query, just get in touch.

Contamination control

We advise you to refer to EU GMP Annex 1 (Guidelines for Sterile Medicinal Products) or ISO 14644-1 (ISO Cleanroom Classification) for the latest particle sizes and maximum concentrations for the appropriate class of cleanroom. Monitoring of particle sizes of 0.5µm and 5.0µm is required for EU-GMP grade cleanrooms. ISO 14644-1:2015 section 4.2 states that one, or more than one, particle sizes can be selected from Table 1 for area classification. Particle sizes can be selected based on process requirements.

When selecting a particle counter, check out the relevant standard to establish the particle size range you need. FMS offers particle counters that start at a particle size range of 0.3µm or 0.5µm as standard, but in specialist cleanrooms, such as those used in semiconductor fabrication applications, 0.1µm and 0.01µm may be necessary.

The next thing to consider is whether you require a portable particle counter for periodic measurements or a remote particle counter for continuous measurements. Remote particle counters are smaller than portable particle counters, allowing them to be discretely mounted in permanent monitoring locations.

The last thing to consider is the flow rate at which the particle counter samples. It can range from 0.1CFM (cubic feet per minute) to 100l/min (litres per minute). Higher flow rates allow a larger volume of air to be sampled in less time, which is beneficial when considering lower particle concentrations. EU-GMP Annex 1 requires a flow rate of at least 1.0CFM (28.3l/min) for continuous monitoring particle counters in Grade A environments.

Particles range in all shapes and sizes. For example, particles visible to the eye are approximately 50-100µm in size. Particle counters are designed to measure particles that you cannot see and have a range of up to 25µm. Particle counters work on the technology of light scattering; the particle enters through the inlet and passes through a laser beam; the particles scatter that laser beam. A detector observes a flash of light and converts it into an electronic signal. The amplitude of this signal relates to an appropriate sizing channel or ‘bin’. Particle counters are calibrated using polystyrene latex (PSL) spheres that are meticulously manufactured and verified for each channel size.


The previous version of Annex 1 from 2008 was 16 pages in length. The update released in August 2022 is 59 pages long, so there’s a lot for manufacturers to get their heads around in time for implementation in August 2023.

There is a focus on the need for a CCS (Contamination Control Strategy) and for QRM (Quality Risk Management), which is used to document all procedures and systems in place to maintain product quality based on a risk assessment of processes. There are now separate sections related to Premises (section 4) and Environmental and Process Monitoring (section 9), which separate the requirements and maximum particle limits for area classification and environmental monitoring.

Guidance for particle counter tubing length has also been introduced, with tubing lengths to be kept under a length of 1 metre unless justified and requiring qualification of both particle counters and associating tubing.

Manufacturers of sterile medicines will be performing a ‘gap analysis’ to identify any requirements from the 2022 revision of Annex 1 that are not met by current systems and procedures. Any new sterile pharmaceutical manufacturing facilities will be designed according to the updated requirements from the 2022 revision of Annex 1. Points relating to monitoring systems, environmental monitoring and particle counters include: 

  • Monitoring Locations
  • Particle Counter Sample Location and Tubing
  • Particle Counter Alert and Action Limits
  • Temperature and Humidity Monitoring
  • Differential Pressure Monitoring
  • Viable Particle Counting throughout setup and processing
  • Real-Time Viable Particle Counting
  • Reporting

Ultimately, the end users of FMS systems are responsible for complying with updated regulatory guidance. However, we have extensive expertise in the field of contamination control measurement and are happy to share that knowledge. Don’t hesitate to get in touch to discuss the implication of this Annex 1 update and other applicable industry standards.

Yes, all new handheld, portable and remote particle counters comply with all the stringent requirements set forth in ISO 21501-4 (Determination of particle size distribution – single particle light interaction methods – Part 4: Light scattering airborne particle counter for clean spaces).

Yes, you can. All relevant cleanroom classifications are preprogrammed into the AeroTrak® 9306 handheld particle counter, all models in the new AeroTrak+® A100 Series of portable particle counters, and legacy AeroTrak® 9000 Series portable particle counter models, allowing you to configure and set limits based on your cleanroom classification standard.

Handheld Particle Counters

The thing to note about handheld particle counters is that, as the name implies, they are for use by hand and have a relatively low flow rate of 0.1 Cubic Feet per Minute (CFM). They are designed for tracking down particle contamination sources, looking for filter leaks and conducting Indoor Air Quality investigations. These are most suitable for application in industries such as Assisted Conception (IVF), Compounding Pharmacies and Cell & Gene Therapy (CGT), for example. While it’s possible to use these particle counters for some classification purposes, the sample volumes that may be required with lower particle concentrations may result in a need for very long sample times, which may be impractical for a handheld instrument.

Remote Particle Counters

Remote particle counters are designed for continuous particle monitoring in conjunction with the FMS 5 software from TSI Inc. AeroTrak+®. Remote Particle Counters are ideal for installation in fixed locations where external vacuum systems are used; such environments are typical of, but not limited to, pharmaceutical, electronics, semiconductor, and industrial facilities. Continuous particle monitoring, where samples are recorded every minute, allows for the analysis of trends throughout all cleanroom operations and can alert in the event of a high particle count. This lets you correlate high particle count events with specific activities or occurrences.

Portable Particle Counters

The new AeroTrak+® Series of portable particle counters was released in March 2023. Although these instruments count particles in the same way as their predecessors, they have received an update to the user interface and appearance, along with some new features. These features include built-in gas correction factors for gas testing, Wi-Fi-enabled connectivity, an LED light bar to indicate machine status and on-device user access controls for GMP Data Integrity (DI) compliance.

Yes, the AeroTrak+® portable particle counters are compatible with the latest version of TSI TrakPro™ Lite Secure software. This will be a different software version from that used with legacy TSI AeroTrak portable and handheld particle counters. The versions of TrakPro Lite Secure software will look slightly different and, for example, the use of recipes has been removed.


TSI’s FMS 5 system is an advanced, reliable, and user-friendly monitoring software suite that features a truly distributed architecture. High availability databases and hot standby system failover functionality assure compliance and peace of mind. Standard inputs include airborne particle counters (multiple manufacturers supported), temperature/humidity, differential pressures, air velocity and digital inputs. Any device that has a linear analog output, OPC-UA communication or volt-free contacts can also be integrated into FMS, including various process-specific metrics, air velocity sensors, VOC concentration and equipment failure alarms. The versatility of FMS 5 makes it popular in a variety of industries from pharmaceutical manufacturing to datacentres, hospital pharmacies and more.

At FMS, we have partnered with industry-leading facility management platform ViGIE to bring you a powerful tool that combines monitoring and maintenance capabilities into a single platform. With real-time equipment monitoring and digital maintenance record, ViGIE enables you to identify issues in real-time to reduce downtime and increase productivity, all within a cloud-based solution. ViGIE monitoring solutions are based on wireless sensor technology with cloud-based data logging and web access, which allows for simplified installation and multi-site transport temperature logging functionality.

AeroTrak 9110

Due to its patented HeNe (Helium Neon) laser technology, the AeroTrak® 9110 portable particle counter offers an accurate measurement of particles down to 0.1μm, with an enhanced signal-to-noise ratio. It is ideal for performing ISO-14644-1 classifications for Class 1 and Class 2 cleanrooms. This makes it a perfect solution for industries operating in ultra-clean environments such as life sciences and electronics applications, including semiconductor.

9001 Condensation Particle Counter

Water! The AeroTrak® Cleanroom Condensation Particle Counter (CPC) Model 9001 is the only water-based, laminar flow, high flow rate instrument on the market – providing the confidence needed for monitoring critical environments. Using patented technology, the instrument provides 10nm sensitivity at a 0.1 CFM (2.83 L/min) flow rate. With an ultra-low false count rate, the AeroTrak 9001 Cleanroom CPC is ideally suited for the low particle concentrations found in ISO Class 1 and Class 2 environments and stringent semiconductor manufacturing and wafer fabrication environments, where nanoscale particle control is crucial.

BioTrak Real-Time Viable Particle Counter

The BioTrak® Biofluorescent Particle Counter (BFPC) instrument has been developed by TSI using its extensive experience in particle measurement and based upon previous generations of particle fluorescence measurement equipment. The BioTrak analyses both particle size and two separate wavelength ranges of particle fluorescence in real time, which provides highly accurate viable particle discrimination. The BioTrak is not a new instrument and has been available for almost a decade, already receiving discrimination algorithm updates based on industry feedback; the latest algorithm update has been used in the 2021 validation study report performed by TSI in order to demonstrate performance when compared to compendial microbial analysis methods.

Alongside this proven real-time viable particle detection technology, the BioTrak samples at 28.3 litres per minute (1CFM) and includes ISO 21501-compliant total particle counting capability. This lets you use the BioTrak as a real-time viable particle counter and a traditional total particle counter at the same time, requiring only one instrument and sample inlet per monitored location.

Yes, you can. While the BioTrak® is an extremely capable stand-alone instrument, able to hold 10,000 sample records in internal memory, it can also be easily integrated into continuous monitoring systems. The BioTrak is designed for continuous monitoring and compatibility with TSI FMS 5 software. This software monitoring solution allows for compliant data logging, real-time alerts, customisable remote data display and report generation. The FMS 5 software suite can also be configured to share data with third-party monitoring and data analysis software packages using the standardised OPC-UA communication protocol.

When combined with an integrated monitoring solution based on FMS 5 software, the BioTrak data can be combined into a complete control and monitoring solution. These customised integrated solutions enable progression to Pharma 4.0 principles, where process data can be shared across multiple analytical and control systems using secure communication. This lets you use combined real-time monitoring data for improved process automation, accelerated decision making and improved process analytics.

No, the BioTrak® instrument does not have the ability to discern between different microorganism species in real time. The BioTrak simply outputs a single value for viable particle count in different size channels; and since microbiological contamination is often attached to other matter in airborne particles, the size cannot be used to differentiate between types of microorganisms, for example bacteria versus mould spores.

However, the BioTrak does include a microbial sample collection filter, which is gelatine based. This filter can be used in combination with agar plate culture techniques to determine species of microorganisms sampled by the BioTrak instrument. This filter sample capture cannot be used for quantification of viable contamination, due to limitations based on filter size and other factors. When implemented, the gelatine filter can be used for samples up to eight hours in duration. Note that the filter and its holder must be handled in a controlled manner to avoid introducing additional contamination to the sample.

The BioTrak Real-Time Viable Particle counter is a three-in-one instrument that includes a 1CFM (28.3L/min) total particle counter, a viability detector and a particle collection plate. The total and viable particle counts are recorded from the same sample using industry-standard volume measurements without normalised data. The 28.3L/min volume of air is then passed through a particle concentrator where excess air is ejected to reduce the sample flow rate into the viability detector. This same air is then passed over a microbial sample collection filter, which allows for the subsequent identification of microorganism species.

No CFUs and AFUs are not comparable, although they cover some of the same microorganisms and show correlated results. This variance is due to the high analysis efficiency of Biofluorescent Particle Counters, which will detect particles with viable characteristics even when compendial methods may have failed to detect them due, for instance, to the particles having been damaged or lost by the collection method, or being otherwise non-culturable. Additionally, there’s the possibility that a small number of non-viable particles may possess fluorescence characteristics which cause them to be detected as viable particles; this can be reduced by testing possible ‘interferent’ materials and the management or elimination of their use in the controlled environment.

It would be required to run the BioTrak® alongside current methods during validation, for baseline determination and to demonstrate method equivalency as set out in the qualification testing procedure advised by TSI Inc.

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