There are many types of microbial air samplers. The most used one is the microbial air sampler based on the impact method on an agar plate (also known as impactor).
This type of sampler has 2 main components: an air pump and a headpiece. The headpiece contains an agar plate. The air pump pulls the air through a perforated cover into the headpiece. The air then makes a short turn above the agar plate. Due to the centrifugal force, the particles in the air make contact with the agar surface and they stick. Micro-organisms always travel on dust or aerosol particles. They rarely travel on their own. By incubating the agar plate after the sampling, the micro-organisms will multiply. After a certain incubation time, the clusters of bacteria are visible on the plate, and the so called colony forming units can be counted. Based on the volume of sampled air, you can then calculate the number of colony forming units present per volume of air. This method is the most used for the so called ‘active air sampling’ or ‘viable particle monitoring’.
What are the advantages of a microbial air sampler by impact on agar?
This method has a large advantage when you do routine microbial quality control of the air. The most common used parameters for this are total viable count, and total yeasts and molds. Usually, you have an idea of the range of colony forming units in the air, and you only want to measure cultivable micro-organisms. Using the microbial air sampler by impact on agar, you have a very fast, easy, and cheap method to monitor the air quality. You sample directly on the plate, incubate, and count it. Culturing is the easiest and a cheap detection method. It is widely used in different industries and guidelines.
What does the EU GMP Annex 1 say about air monitoring?
The EU GMP Annex 1 is a guideline for sterile production (in pharma and biotech production environments). The EU GMP Annex 1 has a section that talks about ‘Viable and non-viable environmental & process monitoring’. Air monitoring is a big part of this section.
The guideline talks about 3 types of air monitoring:
- Passive sampling of viable particles/ settle plates: this is a simulation of what happens in reality. You open the agar plate for max 4 hours, you close it, incubate it, and at the end you can count the colonies.
- Volumetric air sampling / active air sampling of viable particles: this is most often done with an impactor/ microbial air sampler. You sample max 1000L per plate at 100l/min in a cleanroom environment. If you apply continuous monitoring according to the new GMP Annex 1 at for example 25l/min, larger volumes per plate are possible. After that, you incubate the plate, and you count the colonies. This gives you exact data about the number of viable particles per volume of air.
- Monitoring of non-viable particles: for this part, you measure the number of dust particles of <0,5 µm and <5µm using an air sampling instrument (often referred to as particle counters).
For all 3 types of air monitoring mentioned above, the EU GMP Annex 1 defines certain thresholds for the different cleanroom grades: grade A, B, C and D. Also, the frequency of the sampling depends on the cleanroom grade. For grade A zones, the microbial air samples must be in stainless-steel and often satellite samplers or probes are used.
Continuous viable particle monitoring according to the new GMP Annex 1
This is what is written in the GMP Annex 1 at the Chapter n.9:
9.24 Continuous viable air monitoring in grade A (e.g. air sampling or settle plates) should
be undertaken for the full duration of critical processing, including equipment (aseptic set-up)
assembly and critical processing. A similar approach should be considered for grade B cleanrooms
based on the risk of impact on the aseptic processing. The monitoring should be performed
in such a way that all interventions, transient events and any system deterioration would be
captured and any risk caused by interventions of the monitoring operations is avoided.
The culture agar medium is progressively dehydrated and it loses the nutrient characteristics
for specific nutrients for different micro-organisms. The consequence is that the microorganisms
can have difficult to multiplicate and the risk is the difficulty to have the correct colonies count.
It is necessary to adopt an air sampler with a lower air flow rate (e.g.: 25 l/m) and to adopt
Petri dishes with at least a volume of 30 ml of culture agar medium.
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Including:
1x AIRBIO ONE BLUETOOTH Air sampler (100 lts/min) Petri 90 plate with Battery charger 100/240VCA 18VDC 859 mA with adapter for plug Eu/UK/USA - and CABLE for transfer data and 1 calibration certificate
1x s/s ASPI HEAD Petri plate
1x COVER HEAD s/s to protect ASPI HEAD
1x ROBUSTUS MEDIUM carrying case for ARBIO - 56x43x22h cm
Including:
1x AIRBIO ONE BLUETOOTH FILTER air sampler (100 lts/min) Petri plate with Battery charger 100/240VCA 18VDC 859 mA with adapter for plug SHUKO/UK/USA - and CABLE for transfer data, 1 box HEPA Filter and 1 calibration certificate
1x s/s ASPI HEAD Petri plate
1x COVER HEAD s/s to protect ASPI HEAD
1x ROBUSTUS MEDIUM carrying case for ARBIO - 56x43x22h cm
Including:
1x AIRBIO DUO BLUETOOTH Air sampler (100 lts/min) Petri 90 plate with Battery charger 100/240VCA 18VDC 859 mA with adapter for plug Eu/UK/USA - and CABLE for transfer data and 1 calibration certificate
2x s/s ASPI HEAD Petri plate
2x COVER HEAD s/s to protect ASPI HEAD
1x ROBUSTUS MEDIUM carrying case for ARBIO - 56x43x22h cm
