ISO 17225-5:2021

Overview

ISO 17225-5:2021 - "Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood" defines fuel quality classes, dimensional and moisture specifications, and labelling requirements for oven‑ready firewood. The standard applies to firewood from whole trees, stem wood, logging residues and chemically untreated wood industry by‑products. It supports safe, efficient use of graded firewood in residential, small commercial and public building appliances and facilitates clear seller–buyer communication and equipment compatibility.

Key topics and technical requirements

• Fuel classes: Defines classes A1, A2 and B with different dimensional and moisture limits.
  • Moisture content (as‑received, wet basis): A1: 10–20%, A2: 10–25%, B: 10–35% (see ISO 18134‑2 for measurement).
  • A1/A2: suitable for stoves and fireplaces; B: intended for log‑wood boilers.
• Dimensions: Specifies maximum diameters (D classes, e.g. D2, D5, D10…) and standard lengths (L20–L100 with tolerances). Recommended diameter for stoves is <15 cm; D2/D5 are recommended for cookers and kindling.
• Sampling and testing: Sampling, sample preparation and analyses reference ISO 21945, ISO 14780 and other normative methods. Producers may use measured values, calculated typical values or laboratory analysis (simplified or reference methods).
• Energy and density: Energy density can be calculated from bulk density and net calorific value per Annex C. Net calorific value reference: ISO 18125.
• Quality declaration and labelling: Product declarations or package labels must state origin, species, class, moisture, volume/weight unit (stacked/loose m³ or kg) and other relevant properties.
• Contamination and decay: Chemical analysis is generally not required for virgin wood, but testing is mandatory if contamination is suspected. Decay/mould thresholds and split surface quality are addressed.

Practical applications and users

ISO 17225-5 is intended for:

• Firewood producers and suppliers - to classify, pack and label products consistently.
• Retailers and distributors - to verify declared quality and sell by standard units (m³ stacked/loose or kg).
• Appliance manufacturers and installers - to match fuel specifications to stove, fireplace and boiler requirements.
• Testing laboratories and certification bodies - for sampling, moisture and calorific testing.
• Regulators and buyers - to specify procurement criteria for residential and small commercial heating.

Use keywords: ISO 17225-5, graded firewood, solid biofuels, firewood quality, moisture content, fuel classes A1 A2 B, energy density, sampling.

Related standards

• ISO 17225‑1 (general requirements)
• ISO 16559 (terminology)
• ISO 18134‑1/‑2 (moisture determination)
• ISO 14780 (sample preparation)
• ISO 21945 (simplified sampling)
• ISO 18125 (net calorific value)
• Relevant appliance standards referenced in the standard: EN 13229, EN 13240, EN 303‑5, etc.