# Does a workshop lose more air conditioning (AC) gas from small cans or from large cylinders?

Canonical: https://senseible.earth/answers/ac-gas-small-cans-or-cylinders-heel-loss

In its worked example the Intergovernmental Panel on Climate Change (IPCC) assumes 20% of the gas in a small can and 2% of the gas in a cylinder is left behind as a heel and not recovered. The Guidelines say those figures are for example only, so weigh your own containers.

## What the IPCC example assumes

The Guidelines add that wastage levels "will vary substantially" between these supply routes, and that assumptions in the example "are for example only"; compilers should collect country-specific information.

- Bulk containers go to vehicle makers and go back to the refrigerant producer to be refilled, so the example sets their heel at 0%.
- Small cans hold about 300 to 500 grams and are generally used by individuals servicing their own equipment. The example heel is 20%.
- Cylinders hold about 10 to 15 kilograms and are used by shops that service many vehicles. The example heel is 2%.
- The example assumes the heels are not recovered, because the cylinders are discarded and not reused.

## The sum the example uses

Container emissions = 0.02 x gas sold in cylinders + 0.2 x gas sold in small cans. A heel is the vapour or liquid left in a container, which the Guidelines say is "recovered or emitted". The example sets bulk containers at 0% because they go back to the refrigerant producer and are refilled, and treats service cylinders as discarded. If your supplier takes your empty cylinders back and refills them, the heel is recovered; that is our reading, not the Guidelines.

## What to do in your own shop

1. Weigh each cylinder before it goes out and when it comes back, or when you discard it.
2. Ask your supplier whether empty cylinders are taken back and refilled. If they are, the heel is recovered (our reading).
3. Record kilograms lost as a separate line from gas charged into vehicles.
4. Where you have no weighing record, the Guidelines' range of 2% to 10% of the refrigerant market covers transfers and heels together, and is a screening figure only, our reading for a single shop (see the linked page on container handling losses).

## 120 kilograms of AC gas bought a year, two ways

- In 12 kilogram cylinders: 10 cylinders, heel 2% x 120 = 2.4 kilograms lost
- In 400 gram cans: 300 cans, heel 20% x 120 = 24 kilograms lost
- Difference: 24 minus 2.4 = 21.6 kilograms
- At an IPCC Sixth Assessment Report (AR6) global warming potential of 1,530 for hydrofluorocarbon (HFC) HFC-134a: 2.4 x 1,530 = 3,672 kilograms against 24 x 1,530 = 36,720 kilograms of carbon dioxide equivalent (CO2e)

Volumes and container sizes are examples inside the Guidelines' ranges. The 20% and 2% are the Guidelines' example assumptions, not measured values.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into dated records. It does not read recovery notes, service tickets or equipment nameplates, so keep those papers yourself and add the kilograms to your Scope 1 figure.

- [Container handling losses: the IPCC factor](https://senseible.earth/answers/refrigerant-cylinder-handling-losses-ipcc-container-factor)
- [AC gas a car workshop recharges](https://senseible.earth/answers/workshop-car-ac-gas-top-up-scope-1)
- [Turn a top-up invoice into CO2e](https://senseible.earth/answers/refrigerant-top-up-invoice-to-co2e)

Sources: [IPCC 2006 Guidelines, Volume 3, Chapter 7: Emissions of Fluorinated Substitutes for Ozone Depleting Substances](https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_7_Ch7_ODS_Substitutes.pdf), [IPCC Sixth Assessment Report, Working Group I, Chapter 7 Supplementary Material, Table 7.SM.7](https://www.ipcc.ch/report/ar6/wg1/)

Last reviewed 2026-11-05. The 20% and 2% heels are example assumptions in Box 7.4 of the Guidelines. Replace them with your own weighing records.