# We fill metered dose inhalers (MDIs) with a hydrofluorocarbon (HFC) propellant: what counts in our carbon figure?

Canonical: https://senseible.earth/answers/metered-dose-inhaler-hfc-propellant-emissions

Two things can count: propellant lost while you fill (Scope 1, our reading) and propellant in units you sell (Category 11 of the Greenhouse Gas (GHG) Protocol, our reading; confirm with your buyer). The Intergovernmental Panel on Climate Change (IPCC) says aerosol propellant is 100 percent emitted in use.

## The two places the gas goes

- At your plant: charging losses, hoses, rejected units and leftover gas. The IPCC says general aerosol and inhaler manufacturers may be able to provide data on process losses. Reading that for one plant, it is your own direct emission, Scope 1 in GHG Protocol terms (our reading; IPCC does not use Scopes).
- In the units you sell: the IPCC says that during use of aerosols 100 percent of the chemical is emitted. The GHG Protocol's Scope 3 guidance lists HFCs among the greenhouse gases and products that contain or form them and are emitted during use, which it counts in Category 11, use of sold products. Reading an inhaler as such a product is our reading.

## Which gases the IPCC names

The IPCC lists HFC-134a, HFC-227ea and HFC-152a as the HFCs currently used as propellants (in 2006), with MDIs as one of five aerosol sub-applications. It says some inventory compilers report inhaler emissions separately from other aerosols.

## Category 11 for the units you sell

1. For each inhaler type, take the kilograms of propellant in one unit.
2. Multiply by the units sold in the reporting year, not the units filled.
3. Multiply by the share released over the product's life. The GHG Protocol note says if the percentage released is unknown, 100 percent should be assumed.
4. Multiply by the global warming potential (GWP) of each gas. If different gases are used, add the carbon dioxide equivalent of each and sum across products.

## Plant loss: a mass balance (our method)

The sources do not prescribe one for a single plant. A simple check is propellant used (opening stock plus purchases minus closing stock) minus the propellant inside the units you filled. What remains is lost at the plant or left in returned cylinders. Keep the cylinder weights and the fill weight per unit as the evidence.

## One year at an inhaler filling unit (example figures)

- Propellant used: opening 400 plus purchases 3,600 minus closing 500 = 3,500 kilograms
- Units filled: 340,000 at 0.010 kilograms each = 3,400 kilograms inside units
- Plant loss: 3,500 minus 3,400 = 100 kilograms, about 2.9 percent of the propellant used (100 / 3,500)
- Units sold in the year: 300,000 x 0.010 = 3,000 kilograms
- Category 11: 3,000 kilograms x 100 percent released x GWP of the gas
- The 40,000 unsold units hold 400 kilograms (3,400 minus 3,000) and count in the year they are sold

The 0.010 kilogram charge, the stock figures and the unit counts are an example, not typical values. Use the fill weight on your batch records.

## 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 propellant or other fluorinated gas releases from documents, so the plant loss and the Category 11 line come from your own records as shown here.

- [Which year aerosol gas emissions count in](https://senseible.earth/answers/aerosol-hfc-emissions-which-year-sold-or-filled)
- [Scope 3 Category 11 for products you sell](https://senseible.earth/answers/use-of-sold-products-category-11-calculation)
- [Which assessment report's global warming potential values to use](https://senseible.earth/answers/ar5-vs-ar6-gwp-which-to-use)
- [What Senseible does not calculate](https://senseible.earth/answers/what-emissions-senseible-does-not-calculate)

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), [GHG Protocol Technical Guidance for Calculating Scope 3 Emissions, Category 11 (Formula 11.3)](https://ghgprotocol.org/sites/default/files/2022-12/Chapter11.pdf)

Last reviewed 2026-11-05. Section 7.3 of the IPCC 2006 Guidelines predates later propellant choices, so check the gases your product actually uses. Confirm with your buyer or verifier whether they want Category 11 for these units.