How to Eliminate Microbial Contamination from Classified Area : Pharmaguideline

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How to Eliminate Microbial Contamination from Classified Area

Learn the process to effectively remove the microbial contamination from classified areas.
We are receiving a lot of queries from pharmaceutical professionals that they have a lot of contamination in the classified areas. Contamination exceeds grade limits and they have tried everything but unable to get rid of it. Here we shall discuss the effective ways to remove the contamination from the classified areas.

To minimize the contamination, first of all, we have to stop the entrance of the contaminants in the cleanroom area. There are two main possible sources of contamination in a clean room, external environment and human movement.

First of all, check that the HVAC system is validated and also especially check the integrity of all HEPA filters installed in the area. If it is validated recently and found satisfactory then check air changes per hour (ACPH) in the area as per the cleanliness class of the area. Secondly, check the airlocks for their proper operation and cleanliness levels including filter integrity and ACPH. ACPH is the main factor that helps to maintain the cleanliness level of the classified areas.

Personnel working in the classified area must follow the proper gowning system. Gowns and other dress materials must be cleaned and sterile. Garments must be stored in a garment cabinet with UV light. Hands must be disinfected before entering the controlled area.

Elimination of Existing Microbial Contamination
If all the above observations are found satisfactory then you should try to remove existing microbial contamination from the area. An increase in microbial count in a validated classified area shows that we are not following the cleanroom practices properly. It means we are skipping something that must be followed.

There are several ways to minimize the microbial load in the area according to the possible cause of the contamination.

1. HVAC System
Many companies run HVAC systems only in working hours to reduce the operating cost of the company. It is not bad to save the cost but you must “switch on” the HVAC system at least 1 hour before work starts. It will remove the existing contaminants from the area.

If it is your practice and still area has contamination beyond the limits then run the HVAC system continuously and expose the plates once in a day until you get the desired results.

2. Floor Cleaning
All contaminants ultimately settle on the floor from the air, therefore proper floor cleaning is essential to control them. Ideally, the floor in the classified area must be cleaned twice in a shift but if it is insufficient then it should be done thrice.

Additionally, disinfectants used or floor cleaning must be changed on a weekly basis and there should be at least three disinfectants in a rotating cycle. The selection of disinfectants must be done on their mode of action. It means all disinfectants must have a different mode of action. It will help to reduce the chances of development of resistance in microbes.

3. Fogging
Fogging is an effective way to reduce the number of microbes in the controlled areas because it directly affects the microbes present in the air. Fogging also works on the floor, ceiling and walls of the area. The following graphs show a decrease in microbial contamination in the area after fogging.
Disinfectants containing silver nitrate and hydrogen peroxide are used for fogging. Fogging should be carried out for 15-30 minutes and allow the area for 60 minutes to settle down the droplets. The HVAC system should be switched off during this period.
Do not use IPA for fogging as it is flammable and may cause fire in the area.

The above methods are useful in sterile as well as solid oral dosages, where microbial count in the classified area remains towards the higher side. one or more of the above methods can be used to reduce the count to the standard limit.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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  1. Does any regulatory guideline require or suggest a UV light in the dress cabinet?? If there is any, please let me know a reference.


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