SOP for Evaluation of Compressed Air in Manufacturing of Pharmaceutical Products : Pharmaguideline

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SOP for Evaluation of Compressed Air in Manufacturing of Pharmaceutical Products

Standard operating procedure to determine the microbial quality of compressed air used in Pharmaceutical manufacturing.


To lay down a procedure for evaluation of compressed air in the manufacturing of Pharmaceutical products.


This SOP shall be applicable to analyze compressed air microbiologically whether it is suitable for use or not.




Head -QA & QC


5.1 Requirements

5.1.1 Equipment: Flowmeter, 0.45 µ filter papers, sterile pipettes, sterile Petri dishes, filtration unit, an assembly for collecting the sample for microbial analysis.
5.1.2 Media & Chemicals: Sterilized at 121˚C for 20 minutes or as per instructions are given on pack.
  • Soybean casein digest medium (3x100 ml).
  • Soybean casein digest agar
  • MacConkey's agar
  • Levine eosin methylene blue agar 
  • BBS agar
  • TSI agar
  • Xylose lysine deoxycholate agar
  • EE broth 
  • Mannitol salt agar
  • Vogel-Johnson agar
  • Baird Parker Agar 
  • Cetrimide agar
  • Pseudomonas agar(for Pyocyanin & fluorescein) 
  • Violet red bile glucose agar 
  • Rappaport vassiliadis salmonella enrichment medium
  • GN broth
  • Reinforced medium
  • Columbia agar
  • Peptone water
  • Urea broth

5.2 Method

5.2.1 The compressed air is tested for the total viable microbial count.
5.2.2 Clean the flow meter with 70% IPA, allow it to dry properly. Connect one end of the flow meter to the outlet of compressed air, start pressure pump & set flow in such a way that niddle of the flow meter will adjust to 40 (i.e. 40 lit. air/min) & after setting this flow to connect the second end of the flow meter to the flask containing 100 ml sterile soybean-casein digest medium. Allow the air to flow through the medium for 25 min so that 1000 lit air get sampled. Disconnect the flask of SCDM from the flow meter, plug it properly & then tested for the total viable microbial count.
5.2.3 Take out 100 ml from this SCDM in duplicate & filter separately through sterile 0.45 µ filter paper. After each filtration wash the filter paper with 50 ml sterile normal saline.
5.2.4 Keep these filter papers separately on the surface of two sterile solidified soybean casein digest agar plates. Incubate these plates at 30°C-35 °C for 5 days. After incubation count no. of cfu developed on each filter paper. Consider maximum count on SCDA as No. of cfu/1000 lts. of compressed air.
5.2.5 Secondly allow to pass another 1000 lit of this air in 100 ml of sterile Soybean casein digest medium and incubate the medium at 30-35 °C for 24 hours. After incubation carries out detection of Escherichia coli, Salmonella, Pseudomonas aeruginosa & Staphylococcus aureus from soybean casein digest Medium by transferring a loopful from it on the surface of following selective media.
5.2.6 Invert these plates and incubate at 30-35 °C for 48 hours. After incubation observe the plates for colony characteristics (if developed). For further confirmation carry out a confirmatory test or gram staining if necessary. If none of the colonies confirms to the description for respective medium, the compressed air meets the requirement of the test for absence of the respective pathogen.
5.2.7 Compressed air used in the manufacturing of pharmaceutical products must be treated as raw material and due to this at the point of use, it is analyzed microbiologically to determine it's suitability for use.
Related: SOP for Sterility Testing of Compressed Air, Nitrogen and Carbon Dioxide

5.3 Limits

Total microbial count Limit – NMT 100 cfu/m3
Pathogens - Escherichia coli, Salmonella sp., Pseudomonas aeruginosa, Staphylococcus aureus should be absent in 1000 lit.
Note: In each step of the procedure also carry out positive & negative controls along with the test controls.


SOP: Standard Operating Procedure
QA: Quality Assurance
QC: Quality Control
NA: Not Applicable
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