How to select sampling locations for environment monitoring programme?

Environmental monitoring programme is the key factor to check and control the contamination in clean rooms. To get accurate and reproducible results, environment monitoring programme should be sound and justified. In pharmaceuticals clean rooms are classified mainly in to four different grades.

1. Class A

2. Class B 

3. Class C 

4. Class D

How clean rooms are classified?

Clean rooms are classified on the basis for two factors.

(a) Viable count (b) Non viable count

Viable count includes living microbial forms like bacteria, fungus and their spores and non viable count includes particles of  ≥0.5 and 5.0 micron in size. Non viable count or particle count methods have their own limitations. The main limitation of non viable particle count is that it doesn't discriminate between viable and non viable particle. Every particle in the range of  ≥0.5 and 5.0 micron will be considered as a part of non viable particle count if detected by the particle counter. Why we detect 0.5 and 5.0 micron particle size during particle monitoring? This topic I have already explained in one of my blog. In order to implement effective environment monitoring programme, thorough study about clean room is required. Before doing environment monitoring in clean area sampling locations should be decided and justified. This work has to be done during area qualification. The main question is how to select particular sampling location to get accurate and reproducible results because microorganisms are ubiquitous in nature?

How to select sampling location when we have so many locations to choose?

Environment monitoring programme will only give accurate and reproducible results if we choose sampling locations wisely. Proper justification for selection of particular location is required and that should be included in the Risk assessment study for environment monitoring programme. 

In ISO 14644-1, Clean-rooms and associated controlled environment (Part 1- Classification of air cleanliness) formula is mentioned to calculate the number of locations in a particular area for non viable count.

NL = √ A

Where NL is number of locations (rounded up to a whole number)

A is the area of the room in square meter.

This formula might work well for calculating number of locations for non viable particle monitoring but for viable monitoring consideration should be given to the area with higest risk of contamination. We can't apply this formula to calculate the number of locations for viable count. For viable count no formula could work better than the person's own knowledge about the clean area, associated critical factors, major source of contamination etc. This approach is totally based on the risk assessment study. Risk assessment study is basically calculation of qualitative and quantitative risk related to the product which includes magnitude of the risk, probability of that risk and impact of that risk on the product. In clean areas personnel are the major source of product contamination because personnel continuously sheds particles through the skin, mucous membrane and respiratory system. So, consideration should be given to high traffic areas.  So, to select number of sampling location in clean area for viable count, additional risk based assessment study is required in which sampling locations should be selected on the basis of following parameters:

* Select the location where critical product is directly exposed to environment

* Select the locations where probability of finding contamination is maximum 

* Select the locations where movement is maximum/high traffic areas

* Select the location where air flow is not proper

* Select difficult to clean areas

So, these are the major locations where the probability of finding the contamination is maximum and these locations should be selected to get actual data about the clean area. An environmental monitoring programme must cover all the important factors like:

* Sampling locations - Justification for selection of sampling locations

* Frequency of monitoring - When to perform sampling 

* Different monitoring methods - Passive air sampling, Active air sampling, Surface monitoring and Personnel monitoring, 

* Conditions - At rest or in dynamic condition 

* Alert and action limits - Should be decided according to trend of particular area

* Required investigation - In case of any excursion in environmental monitoring count what investigation and CAPA required?
So, these things should be kept in mind while implementing effective environment monitoring programme. Beside this, media plays an important role for the recovery of viable count. For environment monitoring, Soyabean casein digest agar (SCDA) media is commonly used for the recovery of bacteria as well as for fungus because this is the general purpose media and contains all required nutrients for growth of microorganisms. This single media is used for recovery of both type of microorganisms (bacteria and fungus). SCDA media plates are incubated at low temperature as well as at high temperature. For recovery of bacteria high temperature in a range of 30-35°C is required and for the recovery of fungus low temperature in the range of 20-25°C is required. Plates are first incubated at 20-25°C for 72 hours in BOD incubator and then same plates are transferred to 30-35°C for further 48 hours in Bacteriological incubator or vice versa.

Thanks and have a nice day !