2.2 Oxygen-Clean Materials: Delivery, Handling & Recleaning
Key Takeaways
Tubes, valves, fittings, outlets, and other piping components must be cleaned for oxygen service per CGA G-4.1 before installation; fittings may be cleaned by a supplier or agency other than the manufacturer.
Each tube length is delivered plugged or capped by the manufacturer, and all components stay sealed until they are prepared for installation.
Contaminated interiors may be recleaned on site with a hot water and alkaline solution of 1 lb sodium carbonate or trisodium phosphate per 3 gal of potable water, followed by a hot potable water rinse.
Material that is contaminated internally and is not clean for oxygen service must not be installed.
The installer must furnish documentation certifying that the installed piping materials meet the cleaning requirement.
Why Cleanliness Is a Code Requirement
A medical gas pipeline carries oxygen and nitrous oxide straight to patients. Hydrocarbons, cutting oil, pipe-thread dope, dust, or metal chips inside the pipe can ignite in an oxygen stream. They can also be carried into ventilators and anesthesia machines. NFPA 99 handles this risk in two layers: components are cleaned at the factory, and the installer keeps them clean through delivery, storage, cutting, assembly, and testing.
Cleaning Before Installation
NFPA 99 requires tubes, valves, fittings, station outlets, and other piping components to have been cleaned for oxygen service by the manufacturer before installation, following the mandatory requirements of CGA G-4.1, Cleaning Equipment for Oxygen Service. One exception exists: fittings may be cleaned by a supplier or agency other than the manufacturer. This rule covers positive-pressure medical gas components. Valves for any positive-pressure service must likewise be cleaned for oxygen service by the manufacturer.
The installer must furnish documentation certifying that all installed piping materials comply with the cleaning requirement. Keep packing slips, mill certifications, and manufacturer cleanliness certifications with the job records. The verifier and the AHJ may ask for them.
Delivery and Storage
| Item | NFPA 99 delivery rule |
|---|---|
| Tube | Each length delivered plugged or capped by the manufacturer and kept sealed until prepared for installation |
| Fittings, valves, other components | Delivered sealed and labeled, and kept sealed until prepared for installation |
| Metallic flexible joints | Cleaned at the factory for oxygen service and received with certification of cleanliness |
The code does not prescribe a storage rack, but good practice follows from the rules above:
- Keep tube and fittings in a dedicated, dry, covered area away from oils, solvents, thread sealants, and dust-producing trades.
- Store tube off the floor or ground on clean supports, and leave the caps on until the length is cut.
- After cutting a length, recap the remaining tube right away with a clean cap or plug.
- Never tape over the bore. Adhesive residue is exactly the kind of contaminant you are trying to keep out.
Handling During Installation
Several NFPA 99 requirements apply while the system is going together:
- Store and handle to avoid contamination. The interiors of cleaned tubes, fittings, and components must be stored and handled so they are not contaminated before assembly and brazing.
- Examine before joining. Tubes, fittings, valves, and other components must be visually examined internally before they are joined. You are confirming that they have not been contaminated and are free of obstructions or debris.
- Keep openings sealed. During and after installation, openings in the piping system must be kept sealed. This keeps a nitrogen atmosphere in the piping and keeps debris out.
- Use clean tools. The cutting wheels on tube cutters must be free of grease, oil, and any lubricant unsuitable for oxygen service.
- Keep chips out. When deburring, prevent chips from entering the tube.
When Contamination Happens: On-Site Recleaning
NFPA 99 lets the installer reclean, but only within limits.
- Who: the installer, on site.
- What: interior surfaces of tube ends, fittings, and other components that were cleaned for oxygen service by the manufacturer but became contaminated before installation.
- How: thoroughly scrub the interior surfaces with a clean, hot water and alkaline solution of sodium carbonate or trisodium phosphate, mixed at 1 lb (0.5 kg) to 3 gal (11 L) of potable water. Then thoroughly rinse with clean, hot, potable water.
- Alternatives: other aqueous cleaning solutions may be used if they follow the mandatory requirements of CGA G-4.1.
- Fitting sockets: if a socket becomes contaminated before brazing, reclean it for oxygen service as above, then clean it for brazing with a clean, oil-free stainless steel or brass wire brush.
Caution
NFPA 99 also states that material that has become contaminated internally and is not clean for oxygen service shall not be installed. If you cannot reclean a part to oxygen-service condition, such as a long tube with oil throughout its bore, scrap it. Do not install it and hope the purge test will catch the problem.
Related Cleanliness Rules Elsewhere in the Code
- Threaded joints, where permitted, are made up with PTFE tape or another oxygen-service sealant applied only to the male threads. Take care that no sealant gets inside the pipe.
- Leak detectants used in pressure testing must be safe for use with oxygen and contain no ammonia.
- Breaching existing piping, such as tapping into a positive-pressure patient gas or support gas line, may not leave copper particles or debris in the pipe. Any debris must stay contained in the work area.
- Nitrogen NF is the required purge and test gas because it is clean, dry, and oil-free. Compressed shop air is never a substitute.
A Quick Decision Table
| Situation on the job | Correct action |
|---|---|
| Tube bundle arrives with several end caps missing and dust in the bores | Reclean affected ends per NFPA 99, or reject lengths that cannot be returned to oxygen-clean condition |
| Fitting bag torn open in the gang box | Inspect; reclean the socket and interior per the code method before use |
| Cutting oil found inside a cut length | Do not install unless it can be recleaned to oxygen-service condition |
| Brass valve with factory extensions delivered sealed and labeled | Keep it sealed until installation and examine it internally before joining |
Which on-site recleaning method does NFPA 99 describe for contaminated interiors of tube ends and fittings that were factory-cleaned for oxygen service?
Wiping the interior with mineral spirits, then blowing it dry with filtered shop air
Scrubbing with hot sodium carbonate or trisodium phosphate solution (1 lb per 3 gal of water), then a hot potable water rinse
Soaking in acetone and air drying overnight
Flushing with oxygen at normal line pressure until the white cloth test passes, then capping
An installer discovers that a 20 ft length of medical gas tube has oil coating its entire interior, and it cannot be returned to oxygen-service cleanliness. What does NFPA 99 require?
Install it and rely on the initial piping purge test
Install it only on a medical air line
Install it if the verifier's purity test later passes
Do not install it
Which component does NFPA 99 allow to be cleaned for oxygen service by a supplier or agency other than its manufacturer?
Fittings
Tube
Station outlets
Zone valves
Sections you finish are checked off in the contents.