1.0 OBJECTIVE : To lay down a procedure for environmental monitoring of air.

2.0  SCOPE : This SOP shall provide the procedure for monitoring the viable air borne count in unit II.

3.0  RESPONSIBILITY  : Quality Control Executive / Officer.

4.0  ACCOUNTABILITY : Head Quality Assurance.


The microbial environmental conditions of unit II shall be monitored by Settle plate method or air sampling at the locations mentioned.

In case the active air sampler is out of order then settle plate method can be used as alternative for monitoring the microbiological quality of air.


Prepare required quantity of Soyabean Casein Digest Agar media (SCDA) as per SOP. 

Aseptically prepare media plates by adding about 20 to 25 ml of the medium into sterile petri plates of 90 x 15 mm size and allow to solidify under LAF.

Store the prepare media plates in sterile stainless steel containers at a temperature of 22.5°C  ± 2.5°C

For monitoring carry the stainless steel containers with plates into the area where it is to be monitored.

Mark the plates appropriately with the date of sampling, location number, and the method used prior to sampling.

Sterilize the stainless steel aspirating head of the air sampler prior to use by autoclaving as per SOP.

Active Air Sampling:

Analyze the microbial quality of air by sampling 100litres of air at each of the locations mentioned in  using  Active air sampler SAS SUPER 100.

Carry the pre-incubated SCDA plates and sterile SS head in a SS container to the sampling location.

At the sampling location remove the lid of the plate and place the plate in the sterile SS head of the air sampler,

Assemble the SS head on the main body of the air sampler.

Operate the air sampler as per SOP.

After the completion of sampling remove the plate from the SS head, cover with the lid and replace the plate in the SS container.

Carry the container to the Microbiology laboratory and incubate the media plates at  30-35°C for 5 days.

After completion of incubation, count the number of colonies on each plate and record the results as number of CFU/m3   using the below given formula: 

X = Pr x 1000 / V


V  = Volume of sampled air

r   = Colony Forming Units counted on 90 mm plates

Pr = Probable count obtained by positive hole correction

X  = Colony Forming Units per m3 of air  For obtaining the Pr values refer annexure II.

Record the results in annexure

Based on the frequency of air sampling i.e. weekly, monthly, once and once in three months, record the results.


Active air sampling


Settle Plate Method


Bacteria Fungus Bacteria Fungus
Alert limit (For location to be sampled weekly) 100 10 20 02
Alert limit (For location to be sampled monthly, once in

2 month and once in 3 months)

160 16 20 02
 Action Limit (For location to be sampled weekly) 160 16 50 05
Action limit (For location to be sampled monthly, once in

2 month and once in 3 months)

250 25 50 05

In case any of the result crosses the alert limit, inform Head QC/QA, followed by Head Production & Engg.

If the results crosses the alert limits on second day, then inform Head QC/QA followed by Head Production & Engg. and sanitize the area if required.

If the counts exceed the action limits on second consecutive day showing an upward trend, then inform Head QC/QA, followed by Head Production &  Engineering, stop the activities and sanitize the area.

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