ISO 12922 Explained: Requirements for Fire-Resistant Fluids

ISO 12922:2020 specifies minimum requirements for unused HFAE, HFAS, HFB, HFC, HFDR and HFDU fluids in general industrial hydraulics (as of 2026-10-13). Each category must meet the limit values in Table 1, 2 or 3 by the cited test methods. Aerospace, power generation and fluid in service are excluded, and most HFDU fluids count as less flammable, not fire-resistant.

• ISO 12922:2020 is the third edition, published on 2020-02-10 and confirmed after systematic review on 2025-06-25, stage 90.93 (ISO, 2025).

• The 2020 edition revised the water content methods for HFA, HFB and HFC fluids and increased the oxidation requirements for HFDU fluids (ISO 12922:2020, Foreword).

• In HSE hot manifold tests, polyol ester HFDU fluids ignited at 500 °C to 520 °C, against about 420 °C for mineral oil (HSE, 2024).

• FM Approvals Class 6930 makes a fluid with a fire point eligible for approval at a normalized spray flammability parameter of 5 × 10^4 or less (FM Approvals, 2025).

This answer does not cover aerospace or power-generation hydraulic fluids, which ISO 12922 leaves to other requirements, or fluid already in service. It also does not replace site rules: mine regulators and insurers can set their own fire tests and pass limits on top of ISO 12922.

What and whom does ISO 12922 cover?

ISO 12922:2020 covers unused fire-resistant and less flammable hydraulic fluids for hydrostatic and hydrodynamic systems in general industrial use, and it addresses fluid suppliers, end users and hydraulic equipment makers (ISO 12922:2020, clause 1). The scope reads: "This document specifies the minimum requirements of unused fire-resistant and less flammable hydraulic fluids for hydrostatic and hydrodynamic systems in general industrial applications." The same clause says the standard is "not intended for use in aerospace or power-generation applications, where different requirements apply" (ISO 12922:2020, clause 1).

The current edition is ISO 12922:2020, the third edition, published by ISO/TC 28/SC 4 on 2020-02-10 (ISO, 2025). It replaced ISO 12922:2012, which had replaced ISO 12922:1999; both earlier editions are withdrawn (SNV, 2026). ISO closed a systematic review on 2025-06-05 and confirmed the 2020 edition on 2025-06-25, so it stays current at stage 90.93 as of 2026-10-13 (ISO, 2025). No revision project for ISO 12922 appears on the ISO page as of that date.

For a buyer, the scope has two practical limits. ISO 12922 checks a fluid as delivered, not after months in a press or a mining machine. It also sets minimum properties, not a choice of fluid for a given hazard. The standard's introduction states: "It is therefore necessary to know the level of hazard in order to select the appropriate fluid." (ISO 12922:2020, Introduction)

Which fluid categories does ISO 12922 cover?

ISO 12922:2020 covers six of the hydraulic fluid categories that ISO 6743-4 classifies: HFAE, HFAS, HFB, HFC, HFDR and HFDU (ISO 12922:2020, clause 1). ISO 6743-4:2015 is the classification of Family H fluids and excludes automotive brake fluids and aircraft hydraulic fluids (ISO, 2015). ISO 12922 requires that fluids be classified according to ISO 6743-4 before its tables are applied (ISO 12922:2020, clause 5).

The six categories split into water-containing and water-free fluids:

• HFAE is an oil-in-water emulsion and HFAS a chemical solution in water; the 2012 edition described both as typically containing at least 95 % water by mass (ISO 12922:2012, Table 1).

• HFB is a water-in-oil emulsion, typically at least 40 % water by mass, and HFC is a water polymer solution, typically at least 35 % water by mass (ISO 12922:2012, Table 2).

• HFDR fluids are phosphate esters and HFDU fluids are other synthetics, both without water (NSW DPIE, 2019). The most common HFDU fluids are polyol esters (HSE, 2024).

These composition values come from the withdrawn 2012 edition; the 2020 edition details the same six categories (ISO 12922:2020, clause 1), and its tables are in the paid text. Older national classifications list more categories than ISO 12922 details. The NSW resources fact sheet, which classifies fluids under AS 3997.1:1992, also lists HFDS chlorinated hydrocarbons and HFDT mixtures (NSW DPIE, 2019). ISO 12922 sets no requirements for those categories.

What does ISO 12922 require?

ISO 12922:2020 requires each fluid to meet the limit values in one of three tables, chosen by category. Clause 5 reads: "Where applicable and when tested in accordance with the specified methods, fluids shall meet the limit values indicated in Table 1 (HFAE and HFAS fluids), Table 2 (HFB and HFC fluids) and Table 3 (HFDR and HFDU fluids)." The same clause warns that "a significant variation exists in the level of fire-resistance displayed by the different fluid types" (ISO 12922:2020, clause 5).

The standard cites four fire tests: ISO 14935 wick flame persistence, ISO 15029-1 spray flame persistence, ISO 15029-2 stabilised flame heat release, and ISO 20823 hot manifold ignition (ISO 12922:2020, clause 2). Which table row calls which fire test, and the pass limit, sits in the paid text. The wick test does not apply to HFAE and HFAS fluids (ISO 14935:2020, scope).

The table below shows the category-specific test methods that ISO 12922:2020 cites, so you can see which category-specific tests a report for each category should include.

Corrosion protection by ISO 4404-1 applies to all four water-containing categories (ISO 12922:2012, Tables 1 and 2).

For an HFC water glycol, expect the report to include, among other rows, water content, pH by ISO 20843 and the HFC procedure of the TOST ageing test, ISO 4263-2, all cited in ISO 12922:2020, clause 2.

Why are HFDU fluids called less flammable rather than fire-resistant?

HFDU fluids are called less flammable because most of them do not meet the ISO 5598 definition of a fire-resistant fluid, which ISO 12922:2020 applies to HFAE, HFAS, HFB, HFC and HFDR (ISO 12922:2020, clause 1). The standard says: "Most HFDU fluids, while displaying an improvement in combustion behaviour over mineral oil, fall outside this definition" (ISO 12922:2020, clause 1). Fire-resistant fluids are, by definition, difficult to ignite (BSI, 2003).

UK Health and Safety Executive (HSE) tests show where the difference lies. On the ISO 20823 hot manifold, polyol ester HFDU fluids ignited at 500 °C to 520 °C, mineral oil at about 420 °C, and an HFB emulsion at 650 °C to 660 °C (HSE, 2024). In the ISO 15029-2 spray test, the mineral oil and all but one HFDU fluid fell in Class H, the lowest class, with an ignitability factor of 13 or below (HSE, 2024).

HSE concluded that "HFDU fluids provide a clear advantage over mineral oils for the most common risk situation, leaks of fluid onto hot surfaces" (HSE, 2024). Once a spray or pool is burning, the same report found little or no benefit over mineral oil. HSE also found that HFDU fire retardance was maintained over the service life of the samples tested from working machines (HSE, 2024). These results come from a small set of fluids used in British mines and tunnels (HSE, 2024), so they show a pattern, not a rating for any one product.

How do you check ISO 12922 compliance?

You check ISO 12922 compliance by matching the supplier's category and edition to a test report against the right table, then sampling deliveries. ISO 12922 is a product specification, so the evidence is supplier test data and your own tests.

1. Read the technical data sheet. It should name one ISO 6743-4 category and ISO 12922:2020. A claim against ISO 12922:2012 or ISO 12922:1999 refers to a withdrawn edition (SNV, 2026).

2. Ask for the full test report against Table 1, 2 or 3, including the fire tests that table calls for. For HFAE and HFAS concentrates, the 2012 edition required reported results to state the type of test water and the dilution level used (ISO 12922:2012, Table 1).

3. Sample deliveries. ISO 12922 states: "Any drum, barrel, tanker, compartment or any type of container delivered to the end user may be sampled and analysed at the request of the purchaser." Sampling follows ISO 3170 (ISO 12922:2020, clause 4).

4. Settle disputes on results with the precision rules of ISO 4259-2, which ISO 12922 makes mandatory in cases of dispute (ISO 12922:2020, clause 5).

5. Check site and insurer rules separately. In New South Wales, testing should be done by a NATA-accredited laboratory, which must be unrelated to the maker or supplier (NSW DPIE, 2019).

Keep the safety data sheet (SDS) with the test report; the NSW fact sheet asks users to consult the SDS for health effects on exposed workers (NSW DPIE, 2019).

How does ISO 12922 relate to FM Approval and the Luxembourg Report?

ISO 12922 is a product specification, FM Approvals Class 6930 is a certification of spray fire performance, and the 7th Luxembourg Report is a 1994 European mining document, so each is checked on its own. Meeting ISO 12922 does not by itself give FM Approval or mining acceptance.

FM Approvals Class 6930, March 2025 edition, applies to finished industrial fluids used in lubrication, hydraulic power transmission and similar systems (FM Approvals, 2025). A fluid with a fire point is eligible for approval when its normalized spray flammability parameter is 5 × 10^4 or less (FM Approvals, 2025). Use in an application that lets uncertified fluid contaminate a certified one voids the certification for that lot (FM Approvals, 2025). HSE notes the FM test is widely used in the United States because of insurance requirements (HSE, 2024).

The 7th Luxembourg Report, adopted by the Safety and Health Commission on 3 March 1994, set requirements and tests for fire-resistant fluids in European Union proposals for underground mines (ASTM, 1996). The same paper names spray ignition tests and flame propagation or wick tests as the two basic parameters for standardised fire tests (ASTM, 1996).

Regulators can go further. The NSW resources fact sheet sets that an HFDU fluid must not flash or burn on the ISO 20823 manifold below 400 °C (NSW DPIE, 2019).

When should you call a specialist about ISO 12922?

Call a hydraulics or lubrication specialist about ISO 12922 when a fluid decision goes beyond reading a data sheet. Four situations come up often.

• Converting from mineral oil. ISO 12922 warns that it "should also not be assumed that synthetic, non-aqueous fluids can replace mineral oil products without system modifications", and that water-containing fluids may need system design for their use (ISO 12922:2020, Introduction). Draining, flushing and disposal of the old fluid follow its SDS and your local waste rules.

• Choosing between a fire-resistant and a less flammable fluid. Standard fire test results do not settle whether an HFDU fluid is enough where a spray can meet an open flame or spark. HSE reports that HFDU sprays that pass ISO 15029-1 can still burn continuously in other conditions (HSE, 2024).

• Incomplete evidence. A report that skips table rows, omits fire tests or cites a withdrawn edition needs a second look before purchase.

• Several rule sets. Sites that answer to an insurer, a mining regulator and ISO 12922 need one matrix that shows which test meets which rule.

Lubinpla can work an ISO 12922 case from your own TDS, SDS and certificates, set out the conditions, and return one cited document for your review, with your approval at each step.

FAQ

Does ISO 12922 apply to aerospace or power plant fluids?

No. ISO 12922:2020 states that it is not intended for aerospace or power-generation applications, where different requirements apply (ISO 12922:2020, clause 1). The ISO 6743-4 classification behind it also excludes aircraft hydraulic fluids (ISO, 2015). Use the equipment maker's fluid specification for those systems.

Does ISO 12922 cover hydraulic fluid that is already in service?

No. ISO 12922 sets minimum requirements for unused fluid (ISO 12922:2020, clause 1). The standard recommends reading it together with ISO 7745, Hydraulic fluid power: Fire-resistant (FR) fluids: Requirements and guidelines for use (ISO 12922:2020, Introduction).

Can a fire-resistant hydraulic fluid still burn?

Yes. ISO 12922 states: "Even fire-resistant fluids can ignite at very high temperatures and the flammability behaviour of the fluids specified in this document covers a very wide range." (ISO 12922:2020, Introduction). Fire-resistant means difficult to ignite, not non-combustible (BSI, 2003).

Can an HFDU fluid replace mineral oil without changes to the system?

Sometimes, but do not assume it. HSE reports that HFDU fluids can run in standard hydraulic machines with, at most, a change of seals and gaskets (HSE, 2024). ISO 12922 adds that some fluids are incompatible with the elastomers used with mineral oils (ISO 12922:2020, Introduction).

Is EN ISO 12922 the same standard as ISO 12922?

EN ISO 12922:2020 is the European adoption of ISO 12922:2020 (EVS, 2026). National standards bodies publish it under their own prefix, for example SN EN ISO 12922:2020 in Switzerland and NF EN ISO 12922:2020 in France (SNV, 2026). Check that the national edition year is 2020.

Working a case like this? Lubinpla works it from your own documents and site history, step by step with your approval. Free to start, no card.

Sources checked 2026-10-13.

Sources

1. ISO. ISO 12922:2020 Lubricants, industrial oils and related products (class L): Family H (hydraulic systems): Specifications for hydraulic fluids in categories HFAE, HFAS, HFB, HFC, HFDR and HFDU, catalogue page and life cycle. Edition 3, 2020, confirmed 2025. https://committee.iso.org/standard/76807.html

2. ISO. ISO 12922:2020, sample pages (Foreword, Introduction, clauses 1 to 5). Third edition, 2020-02. https://cdn.standards.iteh.ai/samples/76807/99432b814e1f464aaac5821838aadff0/ISO-12922-2020.pdf

3. ISO. ISO 12922:2012, sample pages including Tables 1 and 2 (withdrawn edition). Second edition, 2012. https://cdn.standards.iteh.ai/samples/43284/45541d6c63cc4e5f85d2b5c2177818da/ISO-12922-2012.pdf

4. SNV Swiss Association for Standardization. ISO 12922:2020 listing with version history and adoptions. 2026. https://connect.snv.ch/en/iso-12922-2020

5. ISO. ISO 6743-4:2015 Lubricants, industrial oils and related products (class L): Classification: Part 4: Family H (Hydraulic systems). 2015. https://committee.iso.org/standard/60483.html

6. ISO. ISO 14935:2020 Petroleum and related products: Determination of wick flame persistence of fire-resistant fluids. 2020. https://committee.iso.org/standard/71881.html

7. BSI. BS EN ISO 20823:2003 Petroleum and related products: Determination of the flammability characteristics of fluids in contact with hot surfaces: Manifold ignition test. 2003. https://knowledge.bsigroup.com/products/petroleum-and-related-products-determination-of-the-flammability-characteristics-of-fluids-in-contact-with-hot-surfaces-manifold-ignition-test

8. FM Approvals. Class Number 6930: Examination Standard for Fire Performance of Industrial Fluids. March 2025. https://www.fmapprovals.com/-/media/Feature/Approval-Standards/6930-pdf.pdf

9. Health and Safety Executive (HSE). RR1206 Fire safety: hydraulic systems used in underground work. 2024. https://www.hse.gov.uk/research/assets/docs/rr1206.pdf

10. NSW Department of Planning, Industry and Environment (NSW DPIE). Fact sheet: Testing of fire resistant hydraulic fluids and materials. September 2019. https://www.resources.nsw.gov.au/sites/default/files/documents/fact-sheet-fire-resistant-fluids-to-replace-mdg-3006-mtr-2.pdf

11. ASTM International. Reichel, J. Standardization Activities for Testing of Fire Resistant Fluids, STP16280S. 1996. https://store.astm.org/stp16280s.html

12. Estonian Centre for Standardisation and Accreditation (EVS). EVS-EN ISO 12922:2020, general information and standard history. 2026. https://www.evs.ee/en/evs-en-iso-12922-2020

Written by the Lubinpla team from the sources listed and checked against them before publication.

Reviewed by Jonghwan Moon, Founder & CEO, Lubinpla, 2026-10-14.