Can I subtract the sulphur hexafluoride (SF6) that breaks down in my magnesium furnace from my emissions?
Not under the simple methods of the Intergovernmental Panel on Climate Change (IPCC). Tiers 1 and 2 count all the SF6 used as emitted, although studies show some of it breaks down against hot magnesium. A lower figure needs measured emissions (Tier 3) that include the destroyed SF6 and the secondary gases formed.
What the guidelines say about breakdown
The IPCC guidelines note that it has been a common assumption that SF6 in magnesium cover gas is inert, so essentially all of it is emitted. Recent independent studies, they say, show that SF6 does to a certain degree destruct in contact with liquid or gaseous magnesium at common holding and processing temperatures.
The fraction destroyed, and the type and amount of secondary gas products formed, depend on operating conditions: SF6 concentration in the cover gas, total cover gas flow rate, size of the reactive magnesium surface, type of carrier gas, furnace charging practices and more.
Why you still cannot just take a share off
- Tier 1 and Tier 2 both assume that all SF6 used is subsequently emitted. The guidelines accept this may overestimate, but say the overestimate lies within the overall uncertainty range.
- Part of the destroyed SF6 turns into other fluorinated gases. For Tier 3 the guidelines say it is good practice to include both the destruction of SF6 and the formation of secondary gas products. A figure that only subtracts the destroyed share leaves those gases out.
- The share is specific to a furnace and how it is run, so a figure from a study of another plant is not yours.
What a lower figure needs: Tier 3 measurement
Tier 3 uses actual measured emission data from the individual facility. The guidelines name Fourier Transformed Infra Red Spectroscopy (FTIR) as a typical gas analysis method, with an estimated accuracy of plus or minus 10 percent, and say sampling and calibration problems could raise the overall uncertainty to plus or minus 20 percent.
That is a measurement campaign on your own furnace exhaust, not a calculation from invoices. Until you have one, report the Tier 2 figure and say it is a consumption-based figure that the guidelines accept may overestimate.
Why 27.0 minus a share is not a measurement (example figures)
- SF6 used from cylinder records: 27.0 kilograms. Tier 2 reports 27.0 kilograms emitted.
- A buyer asks why not less. Suppose a paper says 20 percent breaks down: 27.0 x 0.8 = 21.6 kilograms.
- That 21.6 is unsupported. It ignores the secondary gases formed from the 5.4 kilograms (27.0 minus 21.6) that broke down, and it is not your furnace's measurement.
- Report 27.0 now. Report a lower SF6 figure only with your own measured SF6 and secondary gases.
The 20 percent is an example, not a figure from the IPCC. The guidelines give no default for the destroyed fraction.
What Senseible does here
Senseible reads fuel invoices and electricity bills into a dated, fingerprinted record, so the fuel and power of the site show up once uploaded. It does not calculate or measure cover gas releases from documents, so the SF6 line comes from your cylinder records or a measurement of your own exhaust.
- Sulphur hexafluoride in magnesium die casting
- Electronics plant fluorinated gas emissions
- What Senseible does not calculate
Last reviewed 2026-11-05. Based on sections 4.5.1, 4.5.2 and 4.5.3 of the IPCC 2006 Guidelines. If your buyer's or verifier's rule allows a different treatment, follow that rule and state it.