ASTM G93 Oxygen Cleaning: Cleanliness Levels, Methods & Verification for Oxygen-Service Components
> In one line: ASTM G93 is the ASTM International guide that defines cleanliness levels, cleaning methods, and verification techniques for materials and equipment used in oxygen and oxygen-enriched service. It exists because hydrocarbons, oils, particulates and fibers left on a component can ignite in an oxygen-rich atmosphere. G93 tells you how clean a part must be, how to get it there, and how to prove it, and Crestflo offers oxygen / UHP cleaning as a finishing option on instrumentation valves, fittings, tubing and regulators, with heat-number traceability and EN 10204 material test certs.
Scope note: On this site, "oxygen cleaning" means the precision removal of hydrocarbons, particulates and fibers from fluid-system components, fittings, valves, regulators and tubing, so they are safe for oxygen or oxygen-enriched service per ASTM G93. It doesn't cover respiratory-oxygen equipment cleaning. Household or HVAC duct cleaning is excluded too, as is medical-device reprocessing.
Request a quote for oxygen-cleaned components → · sales@crestflousa.com · +1 346 594 9005
Also known as: ASTM G93 designations & oxygen-cleaning terms
Specs, quality plans and purchase orders each write this standard their own way. Whatever term or phrasing shows up below, it points back to the same oxygen-cleanliness guide.
| Category | Terms covered |
|---|---|
| Primary designation | ASTM G93, G93, ASTM G93/G93M, ASTM-G93 |
| Edition call-outs | ASTM G93/G93M-25, ASTM G93-2025, ASTM G93-03, G93-03e1 (historical) |
| Full title | "Standard Guide for Cleanliness Levels and Cleaning Methods for Materials and Equipment Used in Oxygen-Enriched Environments" |
| Level references | ASTM G93 levels, ASTM G93 Level A / B / C / D, oxygen cleanliness levels |
| Synonyms | oxygen cleaning standard, O2 cleaning standard, oxygen-service cleaning standard, cleaned for oxygen service, clean for oxygen service |
| Process phrasings | oxygen cleaning process, oxygen cleaning procedure, oxygen cleaning methods, cleaning methods for oxygen service, hydrocarbon-free cleaning, oil-free cleaning |
| Media phrasings | gaseous oxygen (GOX) cleaning, liquid oxygen (LOX) cleaning, oxygen-enriched atmosphere |
| Level / requirement phrasings | oxygen cleaning levels, oxygen cleanliness levels, oxygen cleanliness standards, oxygen cleaning requirements, oxygen cleaning specification |
| Component phrasings | oxygen cleaning valves, oxygen cleaning fittings, oxygen cleaning tubing, oxygen clean regulators, oxygen-cleaned stainless steel (316L) |
| Concept phrasings | oxygen compatibility, oxygen ignition risk, oxygen-cleaned fittings supplier / manufacturer |
What is ASTM G93?
ASTM G93, currently at revision ASTM G93/G93M-25, is the ASTM International guide titled "Standard Guide for Cleanliness Levels and Cleaning Methods for Materials and Equipment Used in Oxygen-Enriched Environments." ASTM Committee G04 on the Compatibility and Sensitivity of Materials in Oxygen-Enriched Atmospheres maintains it.
The document does three things. First, it lays out a framework of cleanliness levels, how clean a surface needs to be, expressed through allowable nonvolatile residue (NVR) and particulate limits. Second, it walks through cleaning methods suited to different materials and target levels. Third, it covers inspection and verification techniques to confirm the result. It's a guide, not a pass/fail product spec, so it works alongside a purchaser-defined level: you set the level, and G93 tells you how to reach it and how to check your work.
"Cleaned for oxygen service" describes a component that had hydrocarbons, oils, greases, particulates and fibers stripped away to a set level, so it won't ignite or foul an oxygen-rich system. The benchmark is usually ASTM G93 or CGA G-4.1.
Standard at a glance: ASTM G93 attributes
| Attribute | Value (standard published reference) |
|---|---|
| Designation | ASTM G93 / G93/G93M (also written ASTM G 93, G93) |
| Full title | "Standard Guide for Cleanliness Levels and Cleaning Methods for Materials and Equipment Used in Oxygen-Enriched Environments" |
| Issuing body | ASTM International, Committee G04 (materials in oxygen-enriched atmospheres) |
| Document type | Guide (current revision); historically a Standard Practice |
| Current revision | ASTM G93/G93M-25 (2025); prior editions include G93-03 and G93-03e1, cite the edition your specification calls |
| Scope | Cleanliness levels, cleaning methods and inspection/verification for materials and equipment in oxygen and oxygen-enriched service |
| Primary hazard addressed | Ignition of hydrocarbons, oils, greases, particulates and fibers in an oxygen-rich atmosphere |
| Cleanliness-level basis | Allowable nonvolatile residue (NVR) and particulate / particle-size limits |
| Applicable media | Gaseous oxygen (GOX), liquid oxygen (LOX) and oxygen-enriched mixtures |
| Related standards | CGA G-4.1, ASTM G88, ASTM G94, ASTM G63; ASME BPE for high-purity finishes |
Per-level NVR and particulate thresholds are copyrighted material fixed by the current edition of ASTM G93/G93M. This page summarizes the framework; it doesn't reproduce the document itself. Values follow the applicable standard and can be adjusted to fit your requirements.
Why oxygen cleaning matters
Oxygen sharply cuts the ignition energy needed to set off ordinary contaminants. A film of hydrocarbon oil, a bit of lint, a scatter of machining particulate, none of that matters much in plain air, but in an oxygen-enriched system it becomes fuel. Two mechanisms turn this into a real hazard in valves, fittings, regulators and tubing. The first is adiabatic compression: a fast-opening valve compresses downstream gas and heats it in the process. The second is promoted ignition, where a burning contaminant sets the surrounding metal alight. Either way, the result is a fast, high-temperature fire trapped inside a pressurized component.
The main defense is simply getting rid of the fuel: the hydrocarbons, particulates and fibers that G93 targets. That's why oxygen cleanliness gets treated as a specified, verified deliverable, not some housekeeping afterthought. Along with the right choice of alloy, keeping this contamination under control is what keeps oxygen ignition risk manageable and what oxygen compatibility in the finished component really rests on.
Scope of ASTM G93: what it governs and what it does not
ASTM G93 governs the cleanliness of materials and equipment used in oxygen-enriched environments. It spells out which contaminants have to go, how far they need to be reduced, the methods used to get there, and the inspection steps that confirm it all worked.
It is deliberately a guide, not a stand-alone product specification. G93 does not, by itself, pass or fail a part; a purchaser selects a cleanliness level appropriate to the service, and G93 supplies the framework to reach and verify it. Nonmetal seat and seal compatibility for oxygen is evaluated under a separate standard (ASTM G63, nonmetals), and system design under ASTM G88, G93 concerns the cleanliness of the hardware, not the ignition testing of the base materials themselves.
ASTM G93 cleanliness levels: NVR & particulate limits
G93 defines cleanliness through two measurable bases: nonvolatile residue (NVR), the mass of oily/greasy film left per unit area after solvent extraction, and particulate limits, the size and quantity of particles allowed. Levels are commonly identified by letter (Level A, B, C, D and so on), with Level C among those frequently specified in practice. A higher-severity service, higher pressure, higher temperature, or fast-acting valves in gaseous oxygen, calls for a tighter (lower-residue, lower-particulate) level. If you are deciding which cleanliness level you need, work from the service conditions: your system pressure, media (GOX or LOX) and temperature drive the oxygen cleaning levels and requirements your specification should call out.
| Element | Basis | How it is selected |
|---|---|---|
| Nonvolatile residue (NVR) | Allowable residual mass per unit area (e.g. mg/ft² or mg/m²) | Tighter limit for higher pressure / temperature and GOX velocity |
| Particulate / particle size | Allowable particle size and count | Tighter limit for high-purity and fast-acting components |
| Lettered levels (A, B, C, D …) | Named combinations of NVR + particulate limits | Purchaser specifies the level by service severity and media |
The numeric NVR and particulate values behind each lettered level come from the purchased ASTM G93/G93M standard itself, so they aren't reproduced here. Specify the target level on your RFQ. Values follow the applicable standard and can be customized to your requirement.
Cleaning methods under ASTM G93
G93 doesn't hand you a single recipe. It's a toolkit, and you pick the method based on the base material and the target level. The goal never changes though: a hydrocarbon-free, particulate-controlled surface.
| Method | What it removes | Typical material fit |
|---|---|---|
| Aqueous / alkaline wash | Oils, greases, general soils | Stainless and most alloys |
| Solvent degreasing | Hydrocarbons and organic films | Broad; matched to residue type |
| Ultrasonic cleaning | Trapped particulate and film in crevices | Small parts, complex geometries |
| Acid pickling / passivation | Scale, free iron and surface contamination | Stainless and CRA alloys |
| Controlled rinse & dry | Residual cleaning agents and moisture | All, final step before verification |
Method choice matters here: a solvent that works fine on one alloy might ruin another, and the steps run in an order that leaves the final rinse and dry with a surface ready for inspection. Pairing this with electropolish and passivation cuts down the surface area where contaminants can hide, which helps produce a cleaner result.
ASTM G93 verification & inspection methods
A cleanliness level only matters if you can actually prove it. G93 backs its methods up with verification techniques, and each one catches a different kind of residue.
| Method | Detects | Output |
|---|---|---|
| Gravimetric NVR (solvent extraction) | Nonvolatile hydrocarbon / oil residue | Residue mass per unit area vs level limit |
| UV / black-light fluorescence | Fluorescing hydrocarbons and oils | Visual pass / investigate |
| White-light / visible inspection | Visible particulate, fibers, films, water spots | Visual pass / reject |
| Wipe test | Surface film transferable to a clean wipe | Visual / analytical indication |
| Particle count | Particulate size and quantity | Count vs particulate limit |
Crestflo builds cleaning on a documented QA program: in-house NDT, PMI (positive material identification), destructive testing sent out to ISO/IEC 17025-accredited laboratories, and third-party inspection on request. See testing & inspection for details.
ASTM G93 revisions: G93-03 to G93/G93M-25
ASTM revises G93 on a periodic cycle. Over the years the document has moved from a Standard Practice to today's Standard Guide, which reflects its purpose: a framework meant to be used alongside a purchaser-defined level, not a fixed pass/fail rule.
| Edition | Status |
|---|---|
| ASTM G93/G93M-25 (2025) | Current published edition |
| ASTM G93-03 / G93-03e1 | Prior editions (superseded) |
Specify the current revision on every purchase order, and confirm it against the edition named in your project specification. Contract references vary.
ASTM G93 vs CGA G-4.1 & related oxygen-service standards
Buyers routinely ask how G93 compares to CGA G-4.1. Short answer: ASTM G93 is a broad ASTM guide covering cleanliness levels and cleaning methods across materials and equipment, while CGA G-4.1 zeroes in on cleaning equipment for oxygen service in the industrial-gas sector. We get into the finer differences on our CGA G-4.1 page.
| Standard | Governs | Relationship to G93 |
|---|---|---|
| ASTM G93 | Cleanliness levels + cleaning/verification methods | This page |
| CGA G-4.1 | Cleaning equipment for oxygen service (industrial gas) | Companion cleanliness standard, CGA G-4.1 |
| ASTM G88 | Design of systems for oxygen service | System-design companion to G93 cleanliness |
| ASTM G94 | Evaluating metals for oxygen service | Metals-selection companion |
| ASTM G63 | Evaluating nonmetals for oxygen service | Covers seats/seals G93 does not |
| ASME BPE | High-purity / hygienic surface finish | High-purity surface companion, ASME BPE |
Materials for oxygen service: 316/316L, Monel 400 & K500
Alloy choice matters as much as cleanliness in oxygen service. 316/316L stainless works well as the general-purpose pick, 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 evaluated separately, under ASTM G63.
| 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 the full instrumentation-alloy range for other CRA 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 ASTM G93 level. Every part ships with heat-number traceability and an EN 10204 3.1 / 3.2 material test certificate (MTC).
Instrumentation valves, needle, ball, check, bellows and diaphragm, get oxygen-cleaned to whatever level you specify. See our full range.
- Tube fittings, single and double ferrule compression fittings for oxygen service.
- Instrumentation tubing, stainless and alloy tubing built for oxygen and oxygen-enriched lines.
- Pressure regulators, including the high-purity regulator build option.
- Valve manifolds for gauge, sampling and analytical service.
Oxygen and UHP cleaning comes as a finishing option. Specify the G93 revision and target level on your RFQ, and the oxygen / UHP cleaning page walks through how the service gets delivered. These components serve semiconductor, hydrogen, aerospace & defense and analytical sampling applications.
Request oxygen-cleaned components →
Why Crestflo for G93 oxygen-service components
Crestflo makes the valve, fitting, tube or regulator itself and offers oxygen / UHP cleaning as a finishing option, so the part gets cleaned to whatever level your oxygen system needs. One source covers the part and its documented cleanliness.
Every part carries EN 10204 3.1 MTC (3.2 on request) plus a heat number. That's the documentation an oxygen-service QA reviewer expects to see, and it's there on every part, not just some.
Electropolish, passivation and silver anti-galling plating round out the finishing options in scope. Together they support a cleaner, lower-galling surface.
- Lead time that moves projects. Ready stock for standard items, made-to-order for specials, 6–8 week delivery.
Indian-origin material. US or European melt is available on request, and full traceability comes with it, check the origin & TAA position page for details.
- Certified quality system: ISO 9001 / 14001 / 45001 & PED certified.
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. Valve lines qualify to their own standards, ASME B16.34 and the applicable API test standards, while fittings are tested per ASTM F1387; G93 governs the cleanliness, not the pressure qualification. We Engineer Confidence.
How to order oxygen-cleaned parts
Send your requirement over, and the Crestflo Engineering Team will confirm the G93-cleaned component and documentation for your line. Oxygen cleaning cost varies by component, cleanliness level and quantity, so we quote it per RFQ rather than list it.
| Parameter | Example | Why it matters |
|---|---|---|
| G93 revision & level | ASTM G93/G93M-25, Level C | Sets the NVR / particulate acceptance target |
| Component & material | Needle valve, 316L or Monel 400 | Drives cleaning method and ignition resistance |
| Media | GOX or LOX | Influences level and material selection |
| Documentation | EN 10204 3.1 / 3.2 MTC + cleaning cert | Provides the traceable proof of cleanliness |
RFQ, tell us what you need:
- Name
- Company name
- Phone
- Requirement description (component, material, G93 level, media, quantity)
Request a quote for oxygen-cleaned components → · secondary: oxygen & UHP cleaning · talk to an engineer
US contact: sales@crestflousa.com · +1 346 594 9005 · Houston, TX.
Frequently asked questions
What is ASTM G93?
ASTM G93, currently at revision ASTM G93/G93M-25, is ASTM International's guide for cleanliness levels, cleaning methods and verification techniques used with materials and equipment in oxygen and oxygen-enriched environments. ASTM Committee G04 maintains it.
What does "cleaned for oxygen service" mean?
A component has had hydrocarbons, oils, particulates and fibers stripped away to a defined cleanliness level, so it won't ignite or contaminate an oxygen-rich system. That standard is typically CGA G-4.1 or ASTM G93.
What are the cleanliness levels in ASTM G93?
G93 sets cleanliness levels based on allowable nonvolatile residue and particulate limits, often labeled by letter, Level C being one example. The purchaser picks a level according to how severe the service is going to be: pressure, temperature, media. The exact thresholds for each level come from the standard being purchased.
What is the oxygen cleaning procedure?
Degreasing comes first, usually aqueous or alkaline, though solvent works too. Ultrasonic cleaning is optional at this stage. Then acid pickling and passivation, followed by controlled rinsing and drying. Verification closes out the process. The method chosen depends on the base material and how clean the target needs to be.
How is oxygen cleaning verified?
By gravimetric NVR through solvent extraction, UV black-light fluorescence, white-light visual inspection, wipe tests and particle counts. Each technique picks up something different: oily film, fluorescing hydrocarbons, visible particulate or fibers.
ASTM G93 vs CGA G-4.1, what is the difference?
ASTM G93 is a wide-ranging ASTM guide that covers cleanliness levels and cleaning methods across various materials and equipment. CGA G-4.1, by contrast, zeroes in on cleaning equipment for oxygen service within the industrial-gas sector. For a deeper look at how the two compare, see our CGA G-4.1 page.
Which materials suit oxygen service?
Monel 400 and K500 stand up to ignition better, so engineers reach for them in high-pressure, high-velocity gaseous oxygen service. For general-purpose applications, 316/316L stainless remains the standard pick. Nonmetal seals get their own evaluation, following ASTM G63.
Can Crestflo supply oxygen-cleaned valves, fittings, tubing and regulators?
Oxygen and UHP cleaning is available as a finishing option on instrumentation valves, tube and compression fittings, tubing, regulators and manifolds. We clean to your specified G93 level and provide heat-number traceability along with an EN 10204 material test certificate.
What documentation comes with G93-cleaned parts?
Certification: an EN 10204 3.1 (standard) or 3.2 (on request) material test certificate with heat/lot number, plus a cleaning certificate. Note the G93 revision and level on your RFQ, so the documentation lines up with your acceptance criteria.
What lead time applies to oxygen-cleaned components?
Ready stock covers standard items; specials are made to order, with a 6–8 week delivery window. We can handle small MOQs and offer private label too, so send an RFQ with your revision, level and quantity.
Where can I download the ASTM G93 PDF?
ASTM G93 is a copyrighted standard, and ASTM International sells it through its official webstore. We don't host it here. This page summarizes its scope, levels and methods, and it links to related standards for engineering reference.
Are Crestflo oxygen-cleaned parts made in the USA?
Crestflo manufactures for the US market. The standard product comes from India, though US or European melt is available on request, and full material traceability comes standard. For details on origin and TAA, see our US-origin compliance page.
Explore related standards, products & cleaning
Standards: Standards hub · CGA G-4.1 oxygen cleaning · ASME BPE · EN 10204 MTC
Products: Instrumentation valves, tube fittings, instrumentation tubing, pressure regulators and the 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: Semiconductor · Hydrogen · Aerospace & defense · Analytical sampling systems