Fluorinated Gas Inventory Emissions — Methodology and Calculation Approach

This methodology covers the aggregation of a fluorinated-gas inventory under the EU F-Gas Regulation 2024/573, the GHG Protocol and IPCC AR6. It assumes you already know how much of each gas leaked — that upstream step belongs to the refrigerant leakage mass-balance methodology — and focuses on the operation that turns those leaked masses into one defensible Scope 1 figure: the per-gas conversion to CO₂e, the consistent-basis rule that holds the total together, the AR5/AR6 decision, and the blend-GWP trap that silently corrupts inventories. Two worked columns, computed on both bases, make the basis choice concrete.

This methodology is the aggregation layer of the fluorinated-gas cluster. It takes the GWP concept from the glossary, the gas list and reporting obligations from the EU F-Gas Regulation, and the published GWP values from the data layer, and tells you how to combine multiple gases from multiple systems into one consistent Scope 1 total. If you already have leaked masses by gas, jump to the core operation or the worked example.

What an F-Gas Inventory Aggregates

Fluorinated gases are synthetic gases used as refrigerants, electrical insulators, cleaning agents and propellants. They share two properties that make them an accounting category of their own: extremely high global warming potential — hundreds to tens of thousands of times CO₂ — and release through leakage rather than combustion. An F-gas inventory pulls together every such release across an organisation into a single Scope 1 fugitive line.

Four families dominate corporate inventories:

• HFCs (hydrofluorocarbons) — refrigerants in air conditioning, chillers and heat pumps. The largest F-gas source for most organisations.
• PFCs (perfluorocarbons) — niche refrigerants and electronics process gases; very long atmospheric lifetimes.
• SF₆ (sulphur hexafluoride) — the insulating gas in high-voltage electrical switchgear. The highest GWP of any gas in routine industrial use.
• NF₃ (nitrogen trifluoride) — an electronics manufacturing and cleaning gas, shared with the semiconductor process inventory.

The aggregator’s job is narrow and specific: take the leaked mass of each gas, convert each to CO₂-equivalent at a consistent GWP basis, and sum. It does not estimate how much leaked — that is a separate, prior step.

Where the Leaked Masses Come From

This methodology starts from a known leaked mass per gas. Establishing that mass — the activity data — is the subject of a separate methodology, and the boundary between the two is deliberate: each is a single source of truth for its own step.

If you do not yet have leaked masses by gas, start at the mass-balance methodology and return here with the kilograms. Everything below assumes that input is in hand.

The Four Gas Families

Each family spans a wide GWP range, and the gas mix on a given site determines which dominates the total. Representative current (AR6) global warming potentials are shown for orientation; the live reference values are in the GWP table.

The Core Operation: Mass to CO₂-Equivalent

The calculation per gas is a single multiplication; the inventory is the sum of those products. What makes it a methodology rather than a sum is the discipline around the GWP value — which basis, and which source for each gas.

The AR5 / AR6 Basis Decision

GWP values are revised with each IPCC assessment report. The current corporate-reporting basis is AR6 (2021); the previous basis, still seen in older inventories and some regulatory contexts, is AR5 (2014). For most F-gases the two differ by several percent — enough to matter in a total, and enough to make a mixed-basis inventory wrong.

5.1 Why the basis matters

Switching basis moves the single-component gases materially: SF₆ from 23,500 (AR5) to 25,200 (AR6), NF₃ from 16,100 to 17,400, HFC-134a from 1,430 to 1,526, PFC-14 from 6,630 to 7,380. On a high-SF₆ or high-NF₃ site, a basis change shifts the whole inventory by close to ten percent. That is why the basis must be a deliberate, disclosed choice — not an accident of which table someone happened to use.

5.2 The blend trap — and a live inconsistency to watch

Two blends commonly seen in HFC inventories, R-404A and R-410A, appear in two different places in the data with two different values — and this is the single most dangerous thing on this page.

For pure gases the two data families agree exactly. For the two blends they do not: the per-gas table carries a single legacy figure in both basis slots (R-404A 3,922; R-410A 2,088), while the refrigerant data correctly recomputes the blend GWP on AR6 component values (R-404A 4,728; R-410A 2,256) and carries a distinct AR5 figure. The per-gas blend values are neither a correct AR6 figure nor properly basis-differentiated.

5.3 Which basis to report

Use AR6 for all current corporate reporting — the GHG Protocol, CSRD/ESRS E1, CDP and SBTi all expect AR6 GWP-100. Use AR5 only to reconcile against a historical inventory built on that basis, or where a specific regulatory regime still mandates it. Whichever you choose, state it in the inventory and hold it across every gas and every scope. The worked example shows the same site on both bases so the magnitude of the choice is explicit.

Governing Standards

Four reference layers govern F-gas accounting and reporting. They nest from the regulatory obligation, through the inventory boundary, to the GWP science.

GWP Reference Table

Representative current values for the gases most often found in corporate F-gas inventories, surfaced live. Refrigerant values come from the refrigerant dataset, which carries the AR6 figure as its value and the AR5 figure as an alternate on the same row; pure-gas values are confirmed against the per-gas GWP table, with which they agree. Blends are sourced exclusively from the refrigerant dataset for the reasons set out in §5.

Worked Example

A single site leaking four gases, computed on both bases so the basis choice is explicit. Per-gas GWPs render live (drift-proof); only the leaked masses are fixed, and the products are labelled illustrative at the snapshot MasterBrain version. The blends are sourced from the refrigerant dataset, the pure gases from the per-gas table — exactly the sourcing rule from §5.

Per-gas CO₂e is leaked mass × GWP ÷ 1,000 (kg → tonnes). On the AR6 basis MultiGasCo reports 347.232 tCO₂e; on AR5, 314.745 tCO₂e — a difference of 32.487 tCO₂e, or about 10.3%, driven almost entirely by the SF₆ and NF₃ lines where the two bases diverge most. Note the structure of the result: NF₃ at 8 kg contributes more than R-134a at 12 kg, because its GWP is more than ten times higher. In an F-gas inventory the gas mix, not the leaked mass, sets the ranking.

Aggregation Across Sources and Scopes

A real organisation leaks F-gases from several systems, and the aggregator combines them — but only those that belong on the same line. Three boundary rules keep the aggregation clean.

• All operational fugitive F-gas leakage is one Scope 1 line. Refrigerant leakage from cooling, SF₆ from switchgear, NF₃ from on-site processes — all are direct fugitive releases from owned or controlled equipment, so they aggregate into a single Scope 1 F-gas total. The gas families differ; the scope and the accounting do not.
• Process F-gases may belong to a process inventory, not here. Where a site manufactures electronics or semiconductors, the NF₃, SF₆ and PFCs consumed in the process are accounted under the semiconductor etch-gases methodology, which uses a process-specific utilisation-and-abatement method rather than a leakage mass. Decide once which inventory each gas stream belongs to, and do not let a gas appear in both.
• F-gas in sold products is downstream, not Scope 1. Refrigerant charged into a product that leaks during its use phase at the customer is a Scope 3 (use of sold products) emission for the manufacturer, not a Scope 1 fugitive release. Only gas leaking from the organisation’s own equipment is aggregated here.

Rolling the F-gas line up into a full Scope 1 + 2 + 3 corporate total is the job of the GHG inventory aggregator — this page produces the single F-gas figure that feeds it.

Edge Cases

• Blends versus components. A blend such as R-410A can be reported either with its blend GWP applied to the total blend mass, or by decomposing it into component gases (R-32 + R-125) and applying each component GWP. Use one approach consistently; do not mix a blend figure for one charge with a component decomposition for another. The blend GWP from the refrigerant dataset already reflects the mass-weighted component mix.
• Reclaimed and recycled gas. Gas reclaimed from equipment and reused on site is not a fresh purchase and does not itself create an emission — only the fraction that leaks does. The mass-balance methodology handles reclaim on the activity-data side; the aggregator simply converts whatever leaked mass it is given.
• End-of-life recovery. Gas recovered from decommissioned equipment and sent for destruction is not emitted and is not counted. Gas vented at end of life is emitted in full and must be included in the leaked mass. The distinction — like the flaring/venting distinction for methane — turns on whether the gas was destroyed or released.
• Banked gas in equipment. The charge sitting inside operating equipment is a bank, not an emission; it becomes an emission only as it leaks or is vented. Do not report installed charge as emissions — only the leaked fraction.
• Legacy ODS refrigerants. CFCs and HCFCs (R-12, R-22) still in older equipment are ozone-depleting substances controlled under the Montreal Protocol, and their direct CO₂e is often reported for completeness even though they sit outside the Kyoto basket. Report them where required, with their own GWPs, and label them clearly as ODS.
• Unknown or mixed charges. Where the exact refrigerant in old equipment is unknown, identify it from nameplate data or service records before assigning a GWP. Guessing a low-GWP gas where a high-GWP blend is present can understate a line by thousands of times the mass — the highest-leverage uncertainty in the whole inventory.

The Kigali Phase-Down Context

HFC inventories are shrinking by mandate. The Kigali Amendment to the Montreal Protocol commits parties to a stepwise phase-down of HFC consumption, implemented in the EU through the F-Gas Regulation’s declining quota and equipment bans. The trajectory is a falling cap on the CO₂-equivalent of HFCs that may be placed on the market, pushing the market toward low-GWP HFO substitutes such as R-1234yf (GWP ≈ 0.5) and R-1234ze.

The schedule below shows the characteristic shape of the phase-down — a declining quota against a baseline — which is why a well-managed F-gas inventory should trend downward year on year as high-GWP blends are replaced.

For inventory practice this means two things: the gas mix shifts over time toward low-GWP HFOs, dropping the inventory’s CO₂e even at constant leaked mass; and reporting must keep pace with substitutions, because a chiller recharged from R-410A (GWP ≈ 2,256) to R-32 (GWP ≈ 771) or an HFO changes that line’s CO₂e by a factor of three or more. Track the refrigerant actually in each system, not the one it was commissioned with.

Uncertainty and Data Quality

For an F-gas inventory the GWP values are fixed and certain — they are published constants. Essentially all the uncertainty lives on the activity-data side (how much leaked) and in gas identification (which gas it was), both of which sit upstream of this aggregator.

Verification and Assurance

• Basis consistency. The first check: every gas in the F-gas total — and every other line in the wider inventory — is on one declared GWP basis. A mixed AR5/AR6 inventory fails on sight.
• Blend GWP sourcing. Verifiers confirm blend GWPs (R-404A, R-410A, R-407C) were taken from the refrigerant dataset, not a generic per-gas table that may carry an undifferentiated legacy value. An R-410A line at 2,088 rather than 2,256 is a flag.
• Gas identification. Each charge’s gas is substantiated against nameplate or service records, not assumed. Unidentified charges are flagged, not silently assigned a convenient GWP.
• Boundary integrity. No gas appears in both the F-gas line and a process inventory (semiconductor) or a downstream Scope 3 line. Recovered-and-destroyed end-of-life gas is excluded; vented gas is included.
• Leaked-mass provenance. The kilograms feeding this aggregator trace back to the mass-balance or screening method, with the method disclosed per the mass-balance methodology.

The audit framework follows the GHG Protocol Corporate Standard for boundaries and the basis-consistency rule, with the EU F-Gas Regulation 2024/573 supplying the gas list and record-keeping expectations.

Error Traps with Magnitudes

Each error below produces a specific, quantifiable distortion. Magnitudes use the MultiGasCo example (347.232 tCO₂e AR6 total) to make validation and disclosure risk concrete.

Methodology Metadata — for GHG Inventory Documentation

Copy into your GHG inventory methodology statement for inventory-transparency compliance. Adjust the basis and gas-list lines to match your inventory.

Frequently Asked Questions