N.57 – SOP Microbial Compressed Air / Gas Sampling according ISO 8573-7



The purpose of this document is to describe the procedure for compressed air / gas sampling, and reporting of the viable airborne particulates as part of environmental program, using TRIO.BAS GAS Microbial Air Sampler.


This procedure applies for sampling and evaluation of compressed air quality for viable particulates using a Microbiological Air Sampler in Clean Room. The purpose is to certify the absence of microorganisms in 1.000 litres of compressed gas / air.


Agar, Autoclave, Contact Plate, Cleanroom, CFU: Colony Forming Units, Disinfection, Impact, Medium, Petri dish, RABS, SDA: Sabouraud Dextrose Agar, Sterilization, Total Bacterial Count, Tsa: Tryptic Soy Agar

Principle of impact using a Microbiological Air Sampler

Air is aspirated at a fixed speed for a variable time through a cover with small holes. The resulted flow of air is directed on to the agar surface of the contact plate (Petri dish) placed inside the sampler, under the cover with holes. When the preset sample time is completed, the culture plate is removed and incubated for a pre-determined amount of time, and the colony forming units are counted and recorded as CFUs per the volume of measured air.


– ISO 8573-7:2003 Compressed Air – Part 7 – Test method for viable microbiological contaminant content

Abstract ISO 8573-7:2003 specifies a test method for distinguishing viable, colony-forming, microbiological organisms (e.g. yeast, bacteria, endotoxins) from other solid particles which may be present in compressed air. One of a series of standards aimed at harmonizing air contamination measurements, it provides a means of sampling, incubating and determining the number of microbiological particles.

– TRIO.BAS Air Sampler User’s Manual


It is the responsibility of Quality Control Staff to ensure proper operation, maintenance and calibration of Air Sampler per this procedure.

It is the responsibility of Quality Control/Quality Assurance to ensure that all personnel performing this procedure is properly trained.

It is the responsibility of Quality Control Personnel to update and revise this procedure as appropriate.


The safety rules are controlled by the company safety officer.


  • 90 mm Petri dish or 55 mm Contact plates for Total Bacterial Count




  1. Verify the TRIO.BAS GAS and TRIO.BAS MINI air sampler are available and ready to be used. Verify that the paper document for cycle registration is available.
  2. Verify the pressure of the compressed air gas at the output of the gas to analyze is correct according to the TRIO.BAS instruction manual specification.
  3. The aspirating volume of the TRIO.BAS GAS and TRIO.BAS MINI is 100 lts/air per minute and therefore program it for 1.000 litres (10 minutes are necessary for 1.000 litres of air).
  4. The correct adapter must be available to connect the TRIO.BAS GAS to the compressed air/gas output.
  5. Before to start any activity, clean, wash and disinfect with sprayed sterile alcohol the hands. Dress the suitable protective gowns and gloves. All the operations should be aseptically performed applying the GAP (Good Aseptic Procedure).
  6. Prepare the adapter for connection by treating them with sterile alcohol. Make attention to avoid particulates of the Teflon tape are inside the gas tubing.
  7. Verify that the culture plates (Petri or Contact) are correct according to the producer specification (date, quality, etc). Identify each culture plate.
  8. Prepare the surface on which the air sampler will be positioned: 8.1. Cleaned and disinfected surface. 8.2. Sterile dress and gloves. 8.3. Cart on wheel to facilitate the movement of the air sampler inside the Cleanroom.
  9. Position the TRIO.BAS GAS and TRIO.BAS MINI on the cleaned surface, treat all the parts with spray sterile alcohol and complete the assembly. Connect the TRIO.BAS GAS to the gas output.
  10. Clean and disinfect all the surfaces of the air samplers between several sampling cycles.


  1. Insert a culture plate inside the aspiration chamber of the TRIO.BAS MINI. Take out the lid and transfer it on a clean and disinfected surface. Apply the TRIO.BAS MINI to the TRIO.BAS GAS unit.
  2. According to the protocol of the ISO Standard 8573-7, it is necessary to perform a blind test before and after the air sampling (with the air sampler in off condition) to verify that the operator was working in the correct way. The handling of the culture plate is performed as for the real test, but without the compressed gas. The culture plate should be inside the aspiration chamber for 30 seconds. The plate is then transferred for incubation.


  1. Insert a culture plate inside the aspiration chamber of the TRIO.BAS MINI. Take out the lid and transfer it on a clean and disinfected surface. Apply the TRIO.BAS MINI to the TRIO.BAS GAS unit.
  2. Open the valve of the compressed air / gas and, at the same time, switch on the TRIO.BAS MINI. At the end of 1.000 litres of air close the valve and switch off the TRIO.BAS MINI.
  3. Disconnect the TRIO.BAS MINI air sampler, apply the lid to the culture plate and transfer it to incubation.
  4. Transfer the data of the cycles to P.C. by the Bluetooth of the air sampler.


17. 17.1. The culture plates are contaminated before the use. 17.2. The expiration date of the culture plates is over. 17.3. The certificate of the microbial air sampler is expired.