Volatile Matter

What It Measures

Volatile matter is the portion of the sample released as gases and vapours when the fuel is heated out of contact with air — that is, in the absence of oxygen — excluding the moisture determined separately. It captures tars, hydrocarbons and other volatile species driven off during pyrolysis and the early stages of combustion.

For charcoal, residual volatile matter is also an indicator of how completely the original feedstock was carbonised: a more thoroughly carbonised fuel generally retains less volatile material.

Why It Matters

Volatiles govern how readily a fuel ignites and how it behaves in the early phase of burning. They influence flame behaviour, the amount of smoke produced, and the balance between flaming and glowing combustion — all of which matter in cooking, heating and hospitality applications.

Volatile matter is also one of the three measured inputs used to calculate fixed carbon, so it directly affects how the proximate analysis is summarised on a certificate.

Typical Measurement Method

The determination is gravimetric. A weighed sample — typically moisture-free or brought to a specified condition — is heated in a covered crucible or under a controlled inert atmosphere at a temperature and for a time fixed by the method. After volatilisation the crucible is cooled in a desiccator and reweighed, and volatile matter is calculated from the mass lost, excluding the separately determined moisture.

Commonly referenced public methods include ASTM D1762 for wood charcoal, ASTM D3175 for coal and coke, and ISO 18123 for solid biofuels. The furnace temperature, heating rate, residence time and crucible configuration differ between methods and directly affect the result, so the method must accompany any reported value.

Buyer Relevance

Volatile matter helps buyers judge ignition ease and burn behaviour, and how cleanly a charcoal was carbonised. A charcoal with higher residual volatiles tends to flame and smoke more before settling into glowing combustion, which can matter for indoor cooking and for emissions-sensitive uses.

Because volatile matter is an input to fixed carbon and is sensitive to method details, buyers should read it together with the moisture and ash figures and the stated basis, rather than as a stand-alone headline.

Limitations

The result is highly sensitive to heating rate, final temperature, hold time and atmosphere, so values obtained by different methods are not directly comparable. Volatile matter does not identify which species are released.

It is not a measure of smoke or emissions at the point of use — those require combustion testing under a defined protocol (see the emissions methodology). This page describes methodology only and publishes no results.

Data Source

Public standard methodology (general); not supplier-specific test data.

Last updated: 2026-10-07

Public methods commonly referenced

• ASTM D1762 — Chemical analysis of wood charcoal (volatile matter)
• ASTM D3175 — Volatile matter in the analysis sample of coal and coke
• ISO 18123 — Solid biofuels: determination of the content of volatile matter

Standard references are given as general, publicly documented method families. Applicability, current edition and reporting basis must be confirmed with the testing laboratory for any specific report.