CGA G-4.1 Oxygen Cleaning: Cleaning of Equipment for Oxygen Service
CGA G-4.1, "Cleaning of Equipment for Oxygen Service," is the Compressed Gas Association (CGA G) standard covering how to clean components, piping and systems for gaseous and liquid oxygen service. It spells out which contaminants must go, how clean is clean enough, and how you verify and package the result afterward. The point of it all is fire prevention: hydrocarbons, oils and particulate that sit harmlessly in ordinary air can ignite the moment they meet an oxygen-enriched atmosphere. Crestflo offers oxygen / UHP cleaning as a finishing option on instrumentation valves, fittings, tubing and regulators, backed by heat-number traceability and EN 10204 material test certificates.
Scope note: On this page, CGA G-4.1 covers the industrial standard for cleaning fluid-system equipment, fittings, valves, tubing and regulators, for gaseous and liquid oxygen service. It doesn't extend to medical oxygen concentrators, home respiratory devices, HVAC ducting, or oxygen-cylinder refurbishment for medical use.
Request a quote for oxygen-cleaned components → · sales@crestflousa.com · +1 346 594 9005
Also known as: CGA G-4.1 designations & oxygen-cleaning terms
Specs, quality plans and purchase orders label this standard in all sorts of ways. Whatever the wording, the designations below all refer to the same Compressed Gas Association oxygen-cleaning standard.
| Category | Terms covered |
|---|---|
| Primary designation | CGA G-4.1, CGA G4.1, CGA G 4.1, CGA-G-4.1 |
| Edition call-outs | CGA G-4.1-2018 (7th edition), CGA G-4.1 2018, CGA G-4.1-2009 (6th edition) |
| Full title | "Cleaning of Equipment for Oxygen Service" (also cited as "Cleaning Equipment for Oxygen Service") |
| Issuing body | Compressed Gas Association (CGA); also indexed and published through ANSI |
| Synonyms | oxygen cleaning standard, O2 cleaning standard, oxygen-service cleaning standard, oxygen cleaning specification, cleaning equipment for oxygen service |
| Process phrasings | oxygen cleaning process, oxygen cleaning procedure, degreasing for oxygen service, precision cleaning for oxygen service, oil-free cleaning |
| Media phrasings | gaseous oxygen (GOX) service, liquid oxygen (LOX) service, oxygen-enriched environment |
| Requirement phrasings | oxygen cleaning levels, oxygen cleanliness levels, oxygen cleaning requirements, oxygen cleaning verification, oxygen cleaning contamination limits, hydrocarbon limits, particulate limits, nonvolatile residue (NVR) |
| Component phrasings | oxygen cleaned fittings, oxygen cleaned tube fittings, oxygen cleaned valves, oxygen service valve cleaning, oxygen cleaned tubing, oxygen cleaned regulator, oxygen cleaned stainless steel, oxygen-compatible fittings and materials |
| Related-standard phrasings | CGA G-4.1 and ASTM G93, ASTM G93 vs CGA G-4.1, ASTM G93 PDF, EIGA IGC Doc 33, ISO 15001 |
What is CGA G-4.1?
CGA G-4.1, current edition CGA G-4.1-2018 (7th edition), is the Compressed Gas Association standard titled "Cleaning of Equipment for Oxygen Service." It is one of the two references most often called on a US oxygen-service purchase order, alongside ASTM G93, and it is also indexed and distributed through ANSI.
The standard addresses four things. First, the contamination hazards that make oxygen service dangerous: ignitable hydrocarbons, oils, greases, particulate, and fibers a component can carry. Second, acceptable cleaning agents and methods to remove them. Third, cleanliness and acceptance levels, and how to select them by service. And fourth, inspection, verification and packaging, so a cleaned part actually reaches installation still clean. It governs the cleaning of equipment, from single components through complete systems, so it gets applied together with a purchaser-selected cleanliness level rather than as one fixed pass/fail rule.
"Cleaned for oxygen service" means hydrocarbons, oils, particulate matter and fibers have been removed from a component to a defined level, so it won't ignite or contaminate an oxygen-rich system. This is typically specified against CGA G-4.1 or ASTM G93.
Standard at a glance: CGA G-4.1 attributes
| Attribute | Value (standard published reference) |
|---|---|
| Designation | CGA G-4.1 (also written CGA G4.1, CGA G 4.1) |
| Full title | "Cleaning of Equipment for Oxygen Service" |
| Issuing body | Compressed Gas Association (CGA); also indexed via ANSI |
| Document type | Industry standard for cleaning equipment and systems |
| Current edition | CGA G-4.1-2018 (7th edition); prior CGA G-4.1-2009 (6th edition), cite the edition your specification names |
| Scope | Cleaning methods, cleanliness levels, verification and packaging for equipment used in gaseous and liquid oxygen service |
| Primary hazard addressed | Ignition of hydrocarbons, oils, greases, particulate and fibers in an oxygen-enriched atmosphere |
| Cleanliness basis | Nonvolatile residue (NVR), particulate and hydrocarbon limits |
| Applicable media | Gaseous oxygen (GOX) and liquid oxygen (LOX) |
| Related standards | ASTM G93; EIGA IGC Doc 33 and ISO 15001 (European / international equivalents); ASME BPE for high-purity surfaces |
CGA G-4.1 sets the per-level thresholds for NVR, particulate and hydrocarbons, along with the named cleaning agents. It's copyrighted, so this page just summarizes the framework rather than reproducing the document itself. Values follow the applicable CGA G standard and can be customized as needed.
Why oxygen cleaning matters: the ignition hazard
Oxygen sharply lowers the ignition energy of ordinary contaminants. A film of hydrocarbon oil, a fiber of lint, a scatter of machining particulate, none of it would catch in plain air, but in an oxygen-enriched system, it becomes fuel. Two mechanisms make this dangerous in valves, fittings, regulators and tubing. The first is adiabatic compression, where fast-opening flow compresses and heats downstream gas. The second is promoted ignition, where a burning contaminant sets fire to the metal around it. Either way, the result is the same: a rapid, high-temperature fire inside a pressurized component. Removing the fuel is the primary defense here, the hydrocarbons, particulate and fibers CGA G-4.1 targets. That's why oxygen cleanliness, per CGA G, gets treated as a specified, verified deliverable rather than a housekeeping step.
What CGA G-4.1 covers: scope in gaseous and liquid oxygen service
CGA G-4.1 covers cleaning equipment for oxygen service, spanning individual components, piping, valves, and fully assembled systems, in both gaseous oxygen (GOX) and liquid oxygen (LOX) applications. It spells out what has to be removed, the level of cleanliness required, and which methods and agents get you there. It also sets the inspection and packaging steps that confirm and lock in that result.
CGA G-4.1 is written as an industrial standard for the cleaning process, not as a base-material ignition test. Material selection and system design for oxygen service fall under companion references such as ASTM G88 and ASTM G94. The cleanliness-level framework it shares with ASTM G93 defines how clean and how verified. A specification will typically cite CGA G-4.1 (or G93) and name a cleanliness level; from there, CGA G-4.1 supplies the discipline needed to reach it.
| Pillar | What CGA G-4.1 addresses |
|---|---|
| Cleaning methods & agents | Acceptable degreasing and precision-cleaning methods and cleaning agents for oxygen service |
| Cleanliness / acceptance levels | Levels defined through nonvolatile residue, particulate and hydrocarbon limits |
| Inspection & verification | Techniques to confirm a component meets its specified cleanliness level |
| Packaging & labeling | Sealing and marking cleaned parts so cleanliness survives to installation |
CGA G-4.1 cleanliness levels & contamination limits: NVR, particulate & hydrocarbons
Under CGA G-4.1, cleanliness gets measured, not eyeballed. Three yardsticks carry the requirement. Nonvolatile residue (NVR) covers the oily or greasy film left behind per unit area once solvent extraction is done. Particulate sets the size and quantity of particles allowed. And then there's hydrocarbon contamination. Push the service harder, higher pressure, higher temperature, fast-acting valves in gaseous oxygen, and you need a tighter level: lower residue, lower particulate. So if you're trying to figure out which cleanliness level applies, start with the service conditions. System pressure, the media involved (GOX or LOX), and temperature are what drive the oxygen cleaning levels and contamination limits your specification, per CGA G, should spell out.
| Parameter | What it measures | Typical verification method |
|---|---|---|
| Nonvolatile residue (NVR) | Residual oil / grease film mass per unit area (e.g. mg/ft² or mg/m²) | Solvent-extraction gravimetric test |
| Particulate | Allowable particle size and count | White-light inspection, particle count |
| Hydrocarbon residue | Fluorescing hydrocarbons and oils on the surface | UV (black-light) inspection |
The numeric NVR, particulate and hydrocarbon values behind each cleanliness level come from the purchased CGA G-4.1 standard, so we won't reproduce them here. Specify your target level on the RFQ. Values follow the applicable CGA G standard and can be customized to requirement.
Oxygen cleaning process & verification methods under CGA G-4.1
CGA G-4.1 doesn't hand you a single recipe. It lays out a set of acceptable methods, and which one you pick depends on the base material, the geometry, and the target level. The goal never changes: a hydrocarbon-free, particulate-controlled surface, checked and then sealed.
| Stage | Purpose | Notes |
|---|---|---|
| Disassembly | Expose every wetted surface | Components broken down so cleaning reaches all internal geometry |
| Degrease (aqueous or solvent) | Remove hydrocarbons, oils and greases | Method and agent matched to alloy and residue type |
| Rinse | Carry away loosened contaminant and cleaning agent | Controlled-quality rinse water / solvent |
| Dry | Remove residual moisture and solvent | Clean, dry, oil-free gas or controlled drying |
| Inspect & verify | Confirm the specified cleanliness level | UV black-light, white-light, NVR gravimetric, wipe test |
| Package & label | Preserve cleanliness to installation | Sealed / bagged and marked "Cleaned for Oxygen Service" |
On solvents: CGA G-4.1 governs the residue limit rather than mandating one branded chemical. Approved aqueous detergents or oxygen-compatible solvents that leave no residue are used, with the standard's acceptance limits, not the chemical name, deciding whether a part passes. Verification pairs a technique to each residue type: UV black-light fluorescence for hydrocarbons, white-light inspection and particle count for particulate, and a solvent-extraction NVR gravimetric test for oily film, supported by wipe tests. Complementary finishing, electropolish and passivation, reduces the surface area available to trap contaminant and supports a cleaner result.
Packaging & labeling of cleaned parts
A cleaned part meeting CGA G-4.1 standards is only as good as the packaging around it: cleanliness has to survive handling, transport and storage. Technicians seal or double-bag the cleaned components, label them to show they're clean for oxygen service, and leave them sealed until installation. That way no airborne particulate, oil or fiber gets onto the wetted surfaces before the system goes together, in line with CGA G guidance.
CGA G-4.1 vs ASTM G93 & related oxygen-service standards
Buyers routinely ask how CGA G-4.1 sits against ASTM G93. The two aren't rivals; they work together. CGA G-4.1 is the Compressed Gas Association standard for cleaning equipment for oxygen service in the industrial-gas sector. ASTM G93 is the broader ASTM guide that spells out cleanliness levels and cleaning methods used to meet it. A specification will often cite both: one covers the cleaning discipline, the other sets the level framework. European and international programs point to EIGA IGC Doc 33 and ISO 15001 as related oxygen-cleaning documents.
| Standard | Issuing body | What it governs | Relationship |
|---|---|---|---|
| CGA G-4.1 | Compressed Gas Association | Cleaning equipment for oxygen service (methods, levels, verification, packaging) | This page |
| ASTM G93 | ASTM International | Cleanliness levels and cleaning methods for oxygen-enriched environments | Companion standard, ASTM G93 |
| EIGA IGC Doc 33 | EIGA (European Industrial Gases Association) | Cleaning of equipment for oxygen service | European counterpart |
| ISO 15001 | ISO | Anaesthetic and respiratory equipment, compatibility with oxygen | International oxygen-compatibility reference |
| ASME BPE | ASME | High-purity / hygienic surface finish | High-purity surface companion, ASME BPE |
The deeper level-by-level mechanics live on the ASTM G93 page; this page owns the CGA G-4.1 standard itself.
CGA G-4.1 revision history: 6th (2009) to 7th (2018) edition
| Edition | Status |
|---|---|
| CGA G-4.1-2018 (7th edition) | Current published edition |
| CGA G-4.1-2009 (6th edition) | Prior edition (superseded) |
Always specify the current edition on a purchase order, and confirm the edition named in your project specification, since contract references vary. CGA G-4.1 is a copyrighted standard sold by the Compressed Gas Association through its official channels. Get the PDF directly from CGA G; we don't host it.
Materials for oxygen service: 316/316L, Monel 400 & K500
In oxygen service, alloy choice counts every bit as much as cleanliness. 316/316L stainless is the usual pick for general-purpose work, but Monel 400 and Monel K500 win out for high-pressure, high-velocity gaseous oxygen thanks to their resistance to ignition. Nonmetal seat and seal materials get their own treatment in companion oxygen-service references.
| Alloy | UNS | Oxygen-service note | Grade page |
|---|---|---|---|
| 316 / 316L stainless | S31600 / S31603 | General-purpose oxygen-service alloy | 316 / 316L |
| Monel 400 | N04400 | Ignition resistance for high-pressure GOX | Monel 400 |
| Monel K500 | N05500 | Higher-strength nickel-copper for GOX service | Monel K500 |
Crestflo's US material scope covers stainless, high-nickel and corrosion-resistant alloys; brass isn't offered for oxygen-service fittings or valves. Check out the full instrumentation-alloy range for other corrosion-resistant options. Values follow the applicable standard and can be customized to requirement.
Crestflo components available oxygen-cleaned
Crestflo can supply its instrumentation range cleaned to a specified oxygen-service level, with heat-number traceability and an EN 10204 3.1 / 3.2 material test certificate on every part.
| Product family | Oxygen-clean option | Traceability | Link |
|---|---|---|---|
| Tube & compression fittings | Yes, cleaned to specified level | MTC 3.1 (3.2 on request) | Tube fittings |
| Instrumentation valves | Yes, needle, ball, check, bellows, diaphragm | MTC 3.1 (3.2 on request) | Instrumentation valves |
| Pressure regulators | Yes, incl. high-purity build | MTC 3.1 (3.2 on request) | Regulators |
| Instrumentation tubing | Yes, stainless & alloy | MTC 3.1 (3.2 on request) | Tubing |
Oxygen and UHP cleaning comes as a finishing option. Specify the standard you need, CGA G-4.1 or ASTM G93, along with the target level on your RFQ, and the oxygen / UHP cleaning page walks through how the service actually gets delivered. These components go into hydrogen, semiconductor, aerospace & defense, LNG & cryogenic and analytical sampling applications. If you're searching "oxygen cleaning near me" or "CGA G-4.1 near me," Crestflo manufactures in the US with fast lead times. Request an RFQ and note the oxygen-clean option when you do.
Request oxygen-cleaned fittings, valves & tubing → · or request a sample
Why Crestflo for CGA G-4.1 oxygen-service components
Crestflo makes the valve, fitting, tube or regulator itself, then offers oxygen / UHP cleaning as a finishing step, cleaned to whatever level your oxygen system calls for. One supplier covers the part and its documented cleanliness.
Every part carries traceability: an EN 10204 3.1 MTC (3.2 if you need it), plus a heat number stamped on every piece. That's the paperwork an oxygen-service QA reviewer wants to see.
Finishing options round things out. Electropolish, passivation and silver anti-galling plating all help produce a cleaner surface with less galling risk.
- Lead time that moves projects. Ready stock for standard items, made-to-order for specials, 6–8 week delivery.
- Honest origin. Indian origin; US / European melt available on request, with full material traceability. See the origin & TAA position for details.
- Certified quality system: ISO 9001 / 14001 / 45001 & PED certified. We run in-house NDT and PMI, send destructive testing out to ISO/IEC 17025-accredited laboratories, and offer third-party inspection on request.
Crestflo is the instrumentation division of a four-decade-old, Government-of-India-recognized export house with a long Middle-East delivery record, a manufacturing pedigree behind a focused, US-serving instrumentation brand. Fittings are tested per ASTM F1387; valve lines qualify to their own standards, ASME B16.34 and the applicable API test standards, while CGA G-4.1 governs the cleanliness, not the pressure qualification. We Engineer Confidence.
US contact: sales@crestflousa.com · +1 346 594 9005 · Houston, TX.
Frequently asked questions
What is CGA G-4.1?
CGA G-4.1, "Cleaning of Equipment for Oxygen Service," is the Compressed Gas Association standard that lays out cleaning methods, cleanliness levels, verification and packaging for equipment used in gaseous and liquid oxygen service. The current edition, CGA G-4.1-2018 (7th edition), is also indexed through ANSI.
What is oxygen cleaning?
Oxygen cleaning strips hydrocarbons, oils, particulate and fibers from components and systems so they can safely contact gaseous or liquid oxygen without becoming an ignition source. It's not a vague notion of "clean." It's a specified, verified deliverable, defined against standards such as CGA G-4.1 or ASTM G93.
What are the cleanliness standards for oxygen cleaning?
Cleanliness gets judged on three fronts: nonvolatile residue (NVR), particulate limits, and hydrocarbon limits. CGA G-4.1 and ASTM G93 lay out the levels, the methods and how you verify them. The purchaser picks a level based on how severe the service is, pressure, temperature, the media involved, and the actual numeric limits live inside those purchased standards, per CGA G.
What is the oxygen cleaning procedure?
Disassemble first, then degrease (aqueous or solvent), rinse, and dry. From there, inspect and verify using UV black-light, white-light, NVR gravimetric and wipe tests. Seal and label the cleaned parts last. The method chosen depends on the base material and the cleanliness level you're targeting.
What solvent is used for oxygen cleaning?
Approved aqueous detergents or oxygen-compatible solvents that leave no residue are used. CGA G-4.1 sets the residue acceptance limit rather than mandating one branded chemical, so what determines a pass is the measured cleanliness, not the solvent's name.
How is CGA G-4.1 related to ASTM G93?
They are complementary. CGA G-4.1 governs cleaning equipment for oxygen service in the industrial-gas sector; ASTM G93 provides the cleanliness-level and cleaning-method framework used to meet it. Specifications frequently cite both.
Which materials are used for oxygen service?
Monel K500 and Monel 400, along with 316/316L stainless, are the alloys most often used, with the choice driven by pressure and the media involved. Monel tends to win out for high-pressure, high-velocity gaseous oxygen service. The reason comes down to ignition resistance.
Does Crestflo supply oxygen-cleaned fittings, valves and tubing?
Oxygen and UHP cleaning is available as a finishing option on instrumentation tube and compression fittings, valves, regulators and tubing. We clean to whatever level you specify, and every piece comes with heat-number traceability and an EN 10204 material test certificate.
Are Crestflo oxygen-service parts traceable and certified?
Every part comes with a heat/lot number and an EN 10204 3.1 material test certificate (3.2 available on request). The quality system holds ISO 9001 / 14001 / 45001 and PED certification, and testing runs on both fronts: NDT and PMI done in-house, plus destructive testing carried out at ISO/IEC 17025-accredited laboratories.
How do I clean an oxygen concentrator?
CGA G-4.1 governs cleaning industrial oxygen equipment, fittings, valves, tubing, regulators. It doesn't extend to home respiratory devices. Servicing a medical device sits outside CGA G's industrial scope; for that, follow the device manufacturer's instructions instead.
What is the lead time for oxygen-cleaned components?
Ready stock covers standard items; specials are made to order, with delivery running 6–8 weeks. Small MOQs and private label work are both on the table. Send an RFQ specifying your standard, level and quantity.
Where can I get the CGA G-4.1 PDF or CGA G-4.1-cleaned parts?
CGA G-4.1 is a copyrighted standard sold through the Compressed Gas Association's official channels; we don't host it ourselves. When it comes to cleaned hardware, Crestflo serves US customers with fast lead times. Request an RFQ and be sure to specify the oxygen-clean option along with your target level, per CGA G.
Explore related standards, products & cleaning
Standards: Standards hub · ASTM G93 oxygen cleaning · ASME BPE · ASTM F1387 · EN 10204 MTC
Products: Tube fittings · Instrumentation valves · Instrumentation tubing · Pressure regulators · High-purity regulator
Materials: 316 / 316L · Monel 400 · Monel K500 · All alloys
Capability & quality: Oxygen & UHP cleaning · Finishing · Testing & inspection · Traceability · US-origin compliance
Industries we work in: Hydrogen, Semiconductor, Aerospace & defense, LNG & cryogenic, and Analytical sampling systems.