Why must tools used on oxygen equipment be grease-free?

The fire risk

HTM 02-01 (2026) Part B, the NHS England operational guidance, says gaseous oxygen is highly dangerous in contact with oils, greases, tarry substances and many plastics (10.21), and that oil, grease, hand creams, make-up and similar substances, even in minute quantities, are liable to ignite in the presence of high-pressure oxygen or nitrous oxide (10.36). It asks for cylinder valves to be opened slowly to prevent rapid pressurisation, a phase in which ignition may occur by adiabatic compression, particularly in the presence of oil, grease or hand-cream residues (9.164).

WHO's Foundations of medical oxygen systems (2023) notes that oxygen at high pressure, such as in cylinders, can react violently with flammable materials such as oil and grease, and that oil and grease can ignite and burn in oxygen-enriched air. The 2020 WHO interim specification for PSA plants (superseded by WHO's technical specifications of 31 December 2024) warned that oil and grease burn with almost explosive violence when combined with oxygen.

Tools

• HTM 02-01 Part A (15.82), for pipeline installation: only oil-free and grease-free tools and dies should be used.
• HTM 02-01 Part B (9.102): cylinder valves, couplings, regulators, tools, hands and clothing should be kept free from oil and grease.
• WHO (2023): where oxygen systems require maintenance, only tools and substances recommended by the manufacturer should be used.
• Global Fund and Build Health International, PSA plant maintenance tool kit overview (25 April 2025): the kit should be used exclusively for the oxygen system and kept free of grease and dirt at all times, and all service must follow the manufacturer's requirements.
• Global Fund operator procedure template (9 December 2025): only clean, oil-free and non-sparking tools should be used on the plant's oxygen circuit, to avoid any fire risk. Suitable tools avoid damaging sensitive parts such as valves, sensors and fittings and reduce the risk of leaks or oxygen contamination; the template keeps, in Annex K, a separate list of clean oxygen tools reserved for the cylinder-filling booster compressor.

Lubricants, seals and sealing compounds

• WHO (2023): oil and grease must not be used on oxygen equipment, and only lubricants and tapes made specifically for oxygen service should be used. Its cylinder safety signage adds: do not use oil, lubricants or alcohol-based hand sanitiser on cylinder fittings.
• HTM 02-01 Part B: oil and grease should not be used as a lubricant on any gas cylinder or equipment (9.102); lubricants, sealing or jointing compounds should not be used when connecting cylinders to regulators or equipment (9.161); only materials approved for oxygen service should be used (10.21). In its example manifold procedure, an oxygen-compatible leak-detection fluid can be used if in doubt (9.171).
• AIGA 113/20, adopted from EIGA Doc 195 (6.3): lubricants likely to be in contact with oxygen shall be compatible with oxygen, and non-metallic materials, including gaskets, valve packing and compressor piston rings, shall be compatible with oxygen service, taking into account the risk of toxic products if they burn or overheat.
• ISO 15001:2010 addresses cleanliness, resistance to ignition and the toxicity of combustion or decomposition products at the design, manufacturing, maintenance and disposal stages of anaesthetic and respiratory equipment in contact with oxygen.

Cylinders and filling

HTM 02-01 Part B (9.101) asks for cylinders and valves to be kept free from oil, grease and other debris. The Global Fund template asks for all tools, accessories and gloves used with oxygen cylinders to be clean and oil-free, for pigtails to be disconnected with clean nitrile gloves and a clean, oil-free spanner, and, once the protective caps are removed from new cylinders, for an inspection for dust, grease and oil. For cylinder filling, EU GMP Annex 6 (2010, section 30) asks for a visual external inspection of each cylinder and valve for damage and for contamination with oil or grease, with cleaning if necessary; the Annex does not cover hospitals unless this is considered industrial preparation or manufacturing, but relevant parts may be used as a basis.

For the components themselves, see which parts of a PSA plant must be oxygen-compatible, and for pipework, why medical gas pipes must be oxygen-clean.