Buying Precision and Oxygen Service Cleaning

When you need precision or oxygen cleaning

You need it whenever a drawing, system specification or contract states a cleanliness level for a surface, and you always need oxygen service cleaning for parts that will touch oxygen enriched gas or liquid. Machining coolant, thread lubricant, lint and chips are fuel and ignition sources in an oxygen system, and they are contamination in any precision fluid system.

Typical parts that need it:

• Tubing, fittings and manifolds for propellant, pressurant and pneumatic systems on launch vehicles and spacecraft
• Valve bodies, poppets, seats, regulators and filters for liquid oxygen and gaseous oxygen service
• Ground support equipment fluid lines, hoses and panels that connect to flight hardware
• Test stand plumbing and facility components that see oxygen, oxidizers or high pressure gas
• Detail parts that must be cleaned before a clean room assembly step

CGA G-4.1, the industrial gas standard for cleaning oxygen equipment, sets its threshold at surfaces in contact with gas or liquid above 23.5 percent oxygen. Space programs usually go further and set their own levels through the documents in the next section. If you are unsure whether a part needs oxygen cleaning, the answer belongs to your fluid system engineer, and it should be settled before the purchase order, not at receiving.

Which specifications buyers call out

Cite one controlling cleanliness specification and its revision on the PO, plus the level. Each of the common documents was written for a different user, so the right one depends on who owns the hardware and where it will be used.

Program requirements and prime contract flow downs take precedence over all of these. If your contract names one, cite that one. If two documents disagree, settle it with your engineering authority before the order is placed, because a cleaning provider cannot pick between your specifications for you.

For how the CC1246 particle and NVR levels are defined and measured, see our engineering reference on precision and oxygen cleaning. This page sticks to how to buy the service.

Materials compatibility comes before cleaning

A perfectly clean part can still fail in oxygen if a seal, seat, lubricant or coating is not compatible at the system pressure and temperature. Confirm the materials list before you buy cleaning.

NASA-STD-6001 is the NASA standard for flammability, offgassing and compatibility of materials used in space vehicles and their ground support equipment. It includes oxygen tests such as Test 13A, mechanical impact for materials in ambient pressure liquid oxygen, Test 14, pneumatic impact for nonmetals in pressurized gaseous oxygen, and Test 17, upward flammability in gaseous oxygen. Your materials engineer decides which results a part needs. The cleaning source only needs to know the outcome.

What that means for the order:

• List every nonmetal in the assembly, by material and specification, so the cleaner can confirm its solvents and process will not attack it
• State whether soft goods are installed or shipped loose, because many cleaners clean metal details and soft goods separately
• If an oxygen compatible lubricant is applied after cleaning, name the product and who applies it
• Do not let the cleaner substitute a seal or lubricant. Substitutions are engineering changes

Our engineering plastics reference covers the fluoropolymers common in oxygen hardware.

How cleanliness is verified

Verification has two parts: quantitative tests that produce a number you can compare with the required level, and qualitative inspection that catches gross contamination. A certificate should report the numbers, not just a pass.

• Nonvolatile residue. A measured volume of solvent rinses the significant surface, the solvent is evaporated, and the residue is weighed. The result is normalized to surface area and compared with the NVR letter level.
• Particle count. The rinse or flush fluid is filtered and the particles are counted by size range, by microscope or automatic counter, and compared with the particle level.
• White light inspection. Looks for chips, rust, lint and visible films on accessible surfaces.
• Ultraviolet (black light) inspection. Done in a darkened area, it shows many hydrocarbon oils and greases, plus lint, because they fluoresce. Not every oil fluoresces, so UV is a screen, not proof of cleanliness.

The 2025 revision of ASTM G93 separates qualitative methods such as visual and UV inspection from quantitative methods, which matches how most buyers already write requirements: visual and UV must show no contamination, and NVR plus particle count must meet the level.

Two questions to ask any cleaning source up front: what surface area and fluid volume they use to normalize results, and whether they test every part or a representative part from the lot. Either can be acceptable. It just has to match what your specification allows.

Clean room class for cleaning and packaging

The cleaning itself can happen in several areas, but final rinse sampling, drying and the inner bag closure should happen in a controlled environment whose class is stated on the certificate. ISO 14644-1:2015 is the current classification standard.

ISO 14644-1 defines nine air cleanliness classes, ISO Class 1 through ISO Class 9, by the maximum concentration of airborne particles per cubic meter at threshold sizes from 0.1 µm to 5 µm. Lower numbers are cleaner. You will still see the old Federal Standard 209E names on drawings and equipment tags, even though 209E was withdrawn in 2001.

A room class describes the air, not your part. A part packaged in an ISO 7 room can meet a tight CC1246 level, and a part packaged in an ISO 5 bench can still fail one. Ask for both: the room or bench class where packaging happened, and the measured part cleanliness.

How parts should arrive at the cleaner

Send parts to precision cleaning only when every operation that could add contamination is finished. Cleaning is the last wet step before the part is bagged, and anything done after it voids the result.

• Machining, deburr and inspection complete. Burrs that break loose later become particles inside your system.
• Passivation, plating and other finishes already done. Those processes leave residues of their own and belong ahead of precision cleaning on the router. See surface finishing for the processes that usually come first.
• Marking and identification complete. Use a marking method your specification allows for oxygen service, and do it before cleaning.
• No tape, labels or markers on significant surfaces. Adhesive residue left on a surface shows up as nonvolatile residue.
• Ports protected for transit. Clean caps or plugs keep chips and dirt out on the way to the cleaner, even though the cleaner will remove them.
• Assemblies identified as such. Tell the cleaner whether it may disassemble, and who reassembles and retests after cleaning.

Gross pre-cleaning is normally part of the cleaner's process, but heavy cutting fluid, shop dirt or corrosion adds time and risk. If a part arrives with damage or corrosion, the cleaner should stop and report, not clean over it.

Bagging, capping and packaging after cleaning

The package is what keeps the part clean until it reaches your clean area, so specify it as carefully as the level. The common practice is to cap every port with clean closures, bag the part in a clean film, then bag it again so the outer bag can be removed at the clean area entrance while the inner bag stays sealed.

• Film material. Polyethylene, nylon and Aclar fluoropolymer films are all used for cleaned parts, and the choice affects particle shedding, chemical compatibility and how well the bag survives handling. A 2021 ASTM symposium paper compared Nylon 6 and Aclar 22A because no standard method existed to rate how much particulate a bag film sheds in handling. Take the film from your specification or your contamination control engineer, and state it on the PO.
• Closures. Caps and plugs must be clean to the same level as the part and compatible with the service fluid.
• Purge or backfill. Some programs require the inner package or the part's internal volume to be backfilled with clean dry gas before sealing. If yours does, name the gas and its purity specification.
• Labels. Specification, level achieved, cleaning date, lot and certificate number go on the outer bag, never loose inside the inner bag.
• Outer protection. Tubing and long parts need rigid support so the bags are not punctured in transit.

For crating, shock and humidity indicators and carrier choices, see crating and packaging and shipping flight hardware.

Shelf life, broken bags and recleaning

A cleanliness certificate is only valid while the package is intact and within any time limit your program sets. If the inner bag is opened, torn or the closure is disturbed outside a controlled area, treat the part as uncleaned.

The specifications above leave storage time limits to the program, so check your own procedures for how long a cleaned and bagged part may sit before it must be reverified or recleaned. Then put that rule on the PO so the source knows whether to clean now or closer to your need date.

Plan for recleaning in these cases:

• Inner bag damaged or opened before the point of use
• Storage time limit exceeded
• Part reworked, remarked or reassembled after cleaning
• Receiving finds the certificate data does not match the label or the PO level

Recleaning is a new job with new verification and a new certificate. Ask for it to reference the original lot so the part history stays continuous. Our receiving inspection reference explains how to check cleaned parts without opening the inner bag.

Lot travelers and certificates to require

Require a certificate that ties measured results to specific parts. A certificate that only says cleaned for oxygen service, with no level, method or data, cannot be verified and should be rejected at receiving.

Ask for:

• Specification, revision and required level, and the level achieved
• Part number, revision, serial or lot numbers and quantity cleaned
• Verification method, sample fluid and volume, surface area used to normalize results, and whether each part or a representative part was tested
• NVR result and particle counts by size range
• Visual and UV inspection results
• Cleaning date, clean room or bench class where packaging occurred, and the packaging and film used
• A traveler or router showing the operations performed, by date, so the sequence of finishing, marking and cleaning can be audited
• A certificate of conformance to the purchase order, which every order we deliver includes

If the cleaned parts are also new manufacture, keep the material certs and first article report with the cleaning record. Keep those records in the same package so one serial number leads to all of them.

What to put on the purchase order

A PO that names a process instead of a requirement gives the source nothing to verify against. These lines cover what a cleaning source needs to quote and do the job right:

1. Part number, revision and quantity, with serials or lot numbers if they must be tracked
2. Controlling cleanliness specification and revision, and the required level, for example a CC1246 particle and NVR level
3. Service fluid and pressure range, so the source understands what the part will see
4. Nonmetal materials list and whether soft goods are installed
5. Verification required: NVR, particle count, visual and UV inspection, and sampling basis
6. Clean room or bench class required for final sampling and packaging
7. Packaging: closures, film, number of bags, purge gas if required, label content
8. Storage time limit and whether recleaning is in scope
9. Certificate content and any customer or prime flow downs
10. Need date, and whether partial shipments help
11. Export control status of drawings and parts

Drawings for oxygen components on launch and defense programs can be controlled. Our confidentiality page explains how files are handled, and controlled data follows the controlled programs process. The general aerospace RFQ checklist covers the rest of the request.

How a cleaning job flows

Cleaning is usually the last step in a longer chain, so most of the risk sits in the handoffs. A typical sequence:

1. Parts are machined, welded or built, inspected and finished at the manufacturing source
2. Ports are capped and parts are packaged for transit to the cleaning source
3. The cleaner receives, inspects for damage and contamination it cannot remove, and confirms the materials list
4. Pre-clean, precision clean, final rinse and verification sampling
5. Drying, packaging and labeling in the controlled area
6. Certificate review against the PO, then shipment to you or straight to the integration site

When the same order also covers manufacture, the manufacturing source and the cleaning source must agree on how parts move between them, who owns damage in transit, and which document controls the order of operations. That is the coordination a sourcing partner should handle so you are not managing two vendors and a freight carrier for one part number.

Fluid system GSE often needs cleaning to KSC-C-123 or a program level. Our ground support equipment page covers the fabrication side, and our launch providers page covers how we support pad and vehicle programs more broadly.

How Aerospace Sourcing handles precision cleaning

We match your parts to a cleaning source that works to the specification you cite, flow the requirements down and check the paperwork before anything ships. We do not run cleaning lines ourselves, and we do not promise that a source is available for every specification or level.

• One quote, one lead time, one point of contact and one purchase order, even when a machine shop and a cleaning source are both involved
• Your specification, level, verification, packaging and certificate requirements flowed down in writing
• Certificate data compared with the PO and the package labels before shipment
• A certificate of conformance with every order, and the cleaning certificate and other documents your request requires

A person replies within one business day, and rush requests are prioritized. Every supplier signs a flow-down NDA before seeing your files, and suppliers do not learn who the end customer is unless you approve.

Request precision or oxygen cleaning

Send the part list, the specification and the level through the precision cleaning request form. It is preset for cleaning so it asks for the service fluid, materials list and packaging requirements, three details that decide whether a source can take the job and what it will cost. A person will reply within one business day.

Questions

Related

• Ground Support Equipment Fabrication for Launch and Spacecraft Programs
• Sourcing GSE, Pad Hardware and Fluid System Parts for Launch Providers
• Aerospace RFQ Checklist for Machined and Fabricated Parts

Sources

• NASA Technical Standards: MSFC-SPEC-164 Rev E
• NASA Technical Standards: KSC-C-123 Rev J
• ASTM G93/G93M-25 Standard Guide for Cleanliness Levels and Cleaning Methods for Oxygen-Enriched Environments
• SAE: ARP1176 Oxygen System and Component Cleaning and Packaging
• SAE: ARP1176A Oxygen System and Component Cleaning
• CGA G-4.1 Cleaning Equipment for Oxygen Service (ANSI Webstore, 2018 edition)
• NASA Technical Standards: NASA-STD-6001 Flammability, Offgassing, and Compatibility Requirements
• NASA GSFC: product cleanliness levels and IEST-STD-CC1246 history
• ISO 14644-1:2015 Table 1, classes of air cleanliness by particle concentration (reproduction)
• ASTM STP1626: bagging materials for oxygen cleaned parts (Nylon 6 and Aclar 22A)
• WHA International: oxygen cleaning inspection methods, white light and UV
• WHA International: guide to the ASTM G93-2025 revision