Compressed air and process gases
Compressed air · Process nitrogen · Nitrogen overlay · Product-contact gases
The air and gases that touch the product, its containers or its equipment: their specification, the sterilising filter at the point of use, and the checks that they stay clean.
What this page does not claim
An equipment family page teaches how a kind of equipment works and how it is assured. It is not a qualification of any site’s equipment, sets no universal limits, and was checked by SPEQ against the sources it lists, not by an independent engineer.
WHAT IT DOES
Gases such as compressed air and nitrogen push product through filters, overlay filled containers, dry equipment and drive valves. Those that "come in direct contact with the product/primary container surfaces" must be of appropriate chemical, particulate and microbial quality, with oil and water content among the specified parameters (Annex 1, 6.18).
Gases used in aseptic processes pass through a sterilising-grade filter, of nominal pore size no larger than 0.22 µm, at the point of use; pipework after that filter is sterilised, and the gas is monitored for microbes periodically at the point of use (Annex 1, 6.19).
Where it sits: From compressors and gas supplies in the utility area to points of use in formulation, filling, lyophilisation and equipment drying.
WHERE YOU FIND IT
- Pressure transfer of product through sterilising filters
- Nitrogen overlay of aseptically filled containers
- Breaking vacuum in lyophilisers
- Drying and blowing down product-contact equipment
In the reference facility: Plant utilities, HVAC & energy centre, Clean utilities — WFI, clean steam & process gas, Processing & formulation suite, Aseptic filling & isolator line
Not covered on this page: Instrument air that does not contact product or product-contact surfaces; Medical gases supplied as products.
MAJOR COMPONENTS
- Compressor or gas supply (generator, bulk tank, cylinders). Source of the gas; its design affects what the gas can carry (Annex 1, 6.18).
- Dryers and coalescing filters. Remove water and oil to the specification.
- Distribution pipework. Carries gas to users; recorded in drawings with valves, filters and user points (Annex 1, 6.5).
- Point-of-use sterilising-grade filter. 0.22 µm nominal or smaller for aseptic use (Annex 1, 6.19).
- Check valves. Prevent backflow into the product when the system is shut off (Annex 1, 6.20).
Connects to: Filling lines and overlay stations; Lyophilisers; Formulation and holding vessels; Vacuum systems.
INSTRUMENTS AND WHAT THEY MEASURE
- Humidity sensor. Pressure dew point of the gas. Watch for: condensation or peroxide exposure shifting the sensor.
- Oil content test. Oil aerosol and vapour at the point of use. Watch for: sample taken upstream of the point of use.
- Optical particle counter. Particles in the gas at the point of use, through a pressure-reducing diffuser. Watch for: sample tubing long or bent enough to lose large particles.
- Active air sampler and settle plates. Viable contamination of the gas at the point of use, periodically (Annex 1, 6.19). Watch for: media dried out over long exposures.
- Filter integrity tester. Integrity of the point-of-use and vent filters (Annex 1, 6.19). Watch for: membrane not fully wetted, giving a false failure.
PARAMETERS
SETPOINT · MEASURED · LIMIT · ATTRIBUTE- Water content of a gas (pressure dew point) (limit, °C pressure dew point). Specified by the site for the gas’s use and generation system (Annex 1, 6.18).
- Oil content of a gas (limit, mg/m³). Specified by the site for the gas’s use and generation system (Annex 1, 6.18).
- Airborne particle concentration (limit, particles/m³ per size channel). In the gas at the point of use, against the site’s specification.
- Viable airborne contamination (limit, CFU/m³ or CFU/plate per exposure). In the gas at the point of use, against the limit the site defines for the area it is used in.
- Sterilising filter integrity result (limit, bar or psi (bubble point) or mL/min (diffusion, water intrusion)). Point-of-use filters used on a batch basis, and product vessel vent filters, tested and reviewed at batch release (Annex 1, 6.19).
SPEQ publishes no universal alarm or acceptance values: they depend on the process, the product and the site’s own qualification.
CONTROLS, ALARMS AND INTERLOCKS
- Interlock: Backflow prevention. Stops product or contamination flowing back when the vacuum or pressure system is shut off (Annex 1, 6.20).
- Alarm: Dew point or supply pressure out of range. Warns that dryer or supply performance has moved.
- Procedure: Filter integrity at batch release. Batch-use gas filters and vent filters integrity tested, with results reviewed in batch certification (Annex 1, 6.19).
- Procedure: Periodic point-of-use monitoring. Microbial sampling of the gas where it is used (Annex 1, 6.19).
An alarm asks for a response; an interlock stops an action; a safety function protects people and has its own risk basis.
HOW IT FAILS
- Dryer or coalescing filter failure. Water or oil reaches the product or its surfaces.
- Non-integral point-of-use filter. Non-sterile gas enters an aseptic process.
- Unsterilised tubing after the final filter. Contamination added downstream of the filter (Annex 1, 6.19).
- Backflow on shutdown. Product or contamination drawn into the gas or vacuum line (Annex 1, 6.20).
ASSURANCE ACROSS THE LIFECYCLE
EXAMPLES, NOT A MANDATORY LIST- Design. Gas specification by use, including oil and water content (Annex 1, 6.18); Risk classification in the CCS (Annex 1, 6.1, 6.2); Drawings with filters, valves and user points (Annex 1, 6.5).
- Qualification. Point-of-use quality: water, oil, particles and microbes; Filter installation and integrity.
- Routine. Periodic microbial monitoring at points of use; Filter integrity results in batch records; Trend analysis (Annex 1, 6.4).
- Change. Re-testing after compressor, dryer or distribution changes.
WHAT THIS DOES NOT PROVE
- Gas quality at the compressor does not prove quality at the point of use. Instead: Samples taken at the points of use.
- An oil-free compressor does not prove oil-free air. Instead: Oil content measured at the point of use; intake air can carry oil.
- A sterilising-grade filter does not prove the gas reaching the product is sterile. Instead: Its integrity result and the sterilisation of the tubing after it.
SOURCES
2 CITED- EU GMP Annex 1: Manufacture of Sterile Medicinal Products — European Commission (EudraLex Volume 4), 2022 revision, in operation 25 August 2023. EU / EEA; revised jointly with the PIC/S Committee; in force. Supports: Utility risk and records (6.1–6.5); gas quality including oil and water content (6.18); point-of-use sterilising filtration, integrity testing and monitoring (6.19); backflow (6.20).
- EU GMP Annex 15: Qualification and Validation — European Commission (EudraLex Volume 4), 2015. EU / EEA; in force. Supports: The qualification approach for utility systems.
HOW THIS PAGE WAS CHECKED
Researched and checked against the sources above by SPEQ (Claude) on 2026-10-21. It has not been reviewed by an independent engineer. It teaches how this kind of equipment works and is assured; it does not say any site, asset or process is qualified, validated or compliant.
- ISO 8573-1 purity classes are not stated: the standard was not checked from an open copy.
- Vacuum systems are covered here only for backflow; a separate page may follow.
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