BIOTRAK™ REAL-TIME VIABLEPARTICLE COUNTER

IMPORTANCE OF A GOODNON-VIABLE MEASUREMENT

APPLICATION NOTE CC-102

Introduction

A non-viable airborne particle counter is a misnomer. Current airborne particle counting technology such as found in the TSI AEROTRAK™ particle counters, size and count all particles that pass through its viewing volume, it does not matter whether the particle is viable or non-viable. When an airborne particle counter displays 1 particle count at 5 µm it may or may not be viable, the instrument is unable to tell the difference. The great news now is that the BIOTRAK™ Real-Time Viable Particle Counter will be able to tell the difference.

Airborne non-viable particles have been sized and counted using airborne techniques of laser light sources and measuring the scattered light from particles for several decades. The BIOTRAK Particle Counter moves airborne particle counting into the 21st century by using TSI’s patented Laser Induced Fluorescence (LIF) technology to detect viable microbiological particulates in real time. This means end users are immediately notified of the presence of airborne viable particles.

Current FDA Aseptic Processing Guidance 2004 and EU GMP Annex 1:2008 defines non-viable particle count limits and methodologies for particle cleanliness classification and monitoring, directly referencing current ISO 14644-1 and -2 particle air cleanliness standards. The particle counter calibration standard ISO 21501-4 is also linked to these regulatory guidelines as it also references ISO 14644-1. There are currently no guidelines or ISO standards for Classification of viable air cleanliness.

This is exciting new technology and has many advantages. However there are important questions that arise when implementing real-time airborne viable particle counting:

1. How do you ensure a sufficient sample size such that the detection of airborne environmental contaminants is optimized?

2. How do you detect airborne viable particles in real-time, which is clearly useful, and yet at the same time still meet the US and EU aseptic processing regulatory requirements for particle cleanliness?

3. How can you have confidence in the data, particularly when you will compare it to existing historical particle cleanliness trending data which typically spans many years?

Principle of OperationThe FDA guidance clearly states that for environmental monitoring:

“Sample sizes should be sufficient to optimize detection of environmental contaminants at levels that might be expected in a given clean area”.

For this reason TSI has designed the BIOTRAK Viable Particle Counter to have a sample flow rate of 1 CFM. This means that the time taken to sample 1 m³ of air reduced and is comparable with traditional air samplers and airborne particle counters.

The BIOTRAK particle counter comprises four components:

A standard 1 CFM airborne particle counter.

Particle Concentrator.

A particle viability detector using Laser Induced Fluorescence (LIF).

A collection filter for analyzed particle speciation.

The BIOTRAK Particle Counter sizes and counts particles in exactly the same way as conventional airborne particle counters, like the TSI AEROTRAK Portable Particle Counter. The airborne particle counting sensor has a high flow rate of 1CFM (28.3 LPM) and six particle size thresholds ranging from 0.5 µm to 10 µm, and the sensor calibration meets all the requirements of ISO 21501-4. This means that the BIOTRAK Particle Counter can report total particle counts as defined in EU GMP Annex 1 and FDA aseptic processing guidelines and will be directly comparable with historical air cleanliness data.

To be clear: it is possible to use this instrument as a conventional airborne particle counter for both normal classification and process monitoring activities. You can have full confidence in the data collected, and will be able to directly compare it with your historical particle monitoring and classification data.

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Particle Counter

Viability Detector

Particle Concen-

trator

Collection filter

HEPA filter

Viable CountingThe BIOTRAK Particle Counter offers an additional measured parameter, particulate viability. (Another application note covers in detail how the viability detector functions). Particulate viability is reported alongside the conventional total particle count data. To see how the data is presented see the BIOTRAK particle counter user interface below:

T-CNT: Total Count is the total number of particles per volume of air (T-CNT = viable + non-viable). The values shown in the T-CNT column are exactly as they would appear in a conventional airborne particle counter. T-CNT is the number of particles you would report for existing regulatory purposes for both classification and monitoring.

V-CNT: Viable Count: is the total number of viable particles per volume of air.

In this example the instrument is telling us that at ≥ 5µm there is a total count (T-CNT) of 18 particles and 4 of them are viable. At ≥1 µm there is a total count of 872 particles and a viable count (V-CNT) of 54 particles.

Establishing meaningful and comparable airborne viable particle count action and alert limits is an important task and is outside the scope of this application note. However, the current FDA aseptic processing guidance understands that alternate methods for environmental monitoring will require alternate action levels:

“……. You may find it appropriate to establish alternate microbiological action levels due to the nature of the operation or method of analysis.”

Reviewing your historical data will be part of this process; it is extremely helpful to have confidence in the conventional particle count data alongside the new viable particle count data collected by the BIOTRAK instrument. This means that the BIOTRAK instrument data is comparable to your existing historical traditional particle count data and so establishing new viable particle count alert and action limits will be correlated meaningfully to existing trending data.

For example, in Grade C and D (ISO 7 and ISO 8) zones the BIOTRAK Particle Counter will provide important information such as the relationship between the total number of particles and the proportion of viable particles in a clean zone. This will help characterize the environment and could be useful when comparing new airborne viable particle count data with historical environmental and traditional “non-viable” particle count trending data.

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ConclusionThe BIOTRAK Real-Time Viable Particle Counter has been specifically designed to meet the ISO 21501-4 standard so that you can trust the traditional particle count data it delivers. With this instrument, end users can detect airborne viable particles in real time and at a high flow rate with meaningful sample volumes. You can demonstrate with complete confidence, compliance to current particulate cleanliness guidelines and standards, in a single instrument package.

ISO 21501-4 compliance also simplifies the task of comparing new viable particle count data collected by the BIOTRAK particle counter with your existing historical data collected from traditional airborne particle counters.

Importantly, having the conventional particle counting function in the same instrument as a viable detector means that in the cleanroom precious space is saved, the numbers of analytical equipment and the interfaces into critical areas such as isolators is kept to a minimum.

Please contact TSI for more information regarding the BIOTRAK Particle Counter.

TSI Incorporated – Visit our website www.tsi.com for more information.

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