Validation of Compressed Air Systems

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Compressed air systems are a critical component of many pharmaceutical manufacturing facilities. With any new system creation, addition, or change, a validation should be performed to ensure the compressed air is of appropriate quality for its intended use. This validation process must collect enough data to draw scientific evidence that the system quality is appropriate (Senra, Levya, Perez, et. al, 2017). To set up a successful compressed air system validation, it is important to designate specification requirements, timeline, protocols, documents, and training.

Specification Requirements and Testing Parameters

The ISPE Good Practice Guide for process gases asserts that compressed air usage in pharmaceutical manufacturing should be free from contaminants and routinely maintained and tested (2011).

ISO 8573 dictates testing for particles, water, total oil, and microorganisms in compressed air. This standard provides a purity class chart to help users select limits.

Determine the purity limit for each potential contaminant for each process line being validated. There are a variety of quality standards and guidance documents available that can aid in establishing appropriate limits and analytical methods (ISO 8573, USP, ISPE, or CGA).

Particles can be analyzed in a variety of ways. Some specifications require sizing and counting as in ISO 8573-1 Classes 1-5. Alternatively, the weight of the particles via gravimetry is another method to determine contamination levels. Laser particle counters provide instant particle count results and immediate feedback on the quality of the compressed air.

Oil and hydrocarbon requirements may vary depending on specification. Oil vapors and organic solvents are defined by ISO 8573 as a mixture of hydrocarbons composed of six or more carbon atoms. Total oil for ISO 8573 Class 1 and 2 requires the combination of oil aerosol and oil vapor results. A filter and a charcoal tube can be used to test for total oil. If oil mist results are required in the 5-25ppm range, a source bottle vial using GCMS technology is used.

Microbial requirements are also vague and dependent on a risk assessment unique to the facility. Testing for bacteria, yeast, and mold is an important part of ensuring the safety of compressed air used directly and indirectly on products. Further identification of genus and species can allow users to check for certain types of microorganisms that may pose a risk.

Gas purity should be considered during the validation process. If the system requires oxygen, nitrogen, argon, or nitrous oxide, the purity levels can be tested along with contaminants.


Many validations require passing results for several days in a row. In this case, schedule rush results for the first few days of sampling. Laser particle counters can be used for immediate particle results in the field. Water vapor detector tubes can alert users on-site about water contamination issues too.

To determine the sampling schedule and timeline, consider how long each sample will take and how many samples are required at each point. More stringent limits often require a greater air volume.

Sampling Set Up

Ensure there is an appropriate sampling port set up for every point of use in the validation. Consider the materials, the locations, and the ease of access for successful sampling and delay prevention.

Tubing and fittings should be stainless steel or a conductive polymer. Other softer metals and plastics can lead to shedding. Long permeable hoses can result in water contamination. Seals should be welded or use stainless steel. Putty and PTFE tape are known to shed and should be avoided at sampling points. Use particle-free stainless steel valves or have stainless steel shut-offs.

A thorough purging of system piping before sampling is essential in avoiding particle contamination from construction, installation, or modification of the piping.

Documentation and Training

Documentation and training certificates must be recorded and stored for each validation. Chain of custody, training documents, calibration certificates, and analysis reports should be organized and completed.

A third-party laboratory can provide you with calibration certificates and training modules. Thorough completion of data sheets will result in quick and succinct reports.


When performing a validation of a new or modified compressed air system, identify the specification requirements, sampling timeline, and required materials for successful testing. Working with a third-party accredited laboratory that specializes in compressed air and gas testing makes the process straightforward. For more information, please contact Trace Analytics via or phone: 512-263-0000 ext 5.


  1. Ochoa, R. (n.d.). Sampling and testing for compressed air contaminants. Compressed Air Best Practices. Retrieved January 18, 2022, from
  2. Senra, A., Leyva, A., Pérez, G., Bisquet, I., Montané, M., Valdés, R., Robles, S., & Cruz, T. de la. (2017, December 12). Qualification and continuous validation of a compressed air system used in the biotechnological industry. IVT. Retrieved January 4, 2022, from
  3. Hagopian, Brian, et al. Good Practice Guide: Sampling for Pharmaceutical Water, Steam and Process Gases, ISPE, 2016.
  4. Larrabee, Chad, and Nicholas Haycocks. ISPE Good Practice Guide: Process Gases. ISPE, 2011.