EN ISO 17225-5:2026

Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood (ISO 17225-5:2026)

This document specifies the fuel quality classes and specifications of graded firewood. This document applies only to firewood produced from the following raw materials (see ISO 17225-1:2021, Table 1):
1.1.1 Whole trees without roots;
1.1.3 Stemwood;
1.1.4 Logging residues (thick branches, tops, etc.);
1.2.1 Chemically untreated by-products

Biogene Festbrennstoffe - Brennstoffspezifikationen und ‑klassen - Teil 5: Klassifizierung von Stückholz (ISO 17225-5:2026)

Dieses Dokument legt die qualitätsbezogenen Brennstoffklassen und -spezifikationen von klassifiziertem Stückholz fest. Dieses Dokument gilt nur für Stückholz, das aus folgenden Rohmaterialien hergestellt wurde (siehe ISO 17225 1:2021, Tabelle 1):
   1.1.1 Vollbäume ohne Wurzeln;
   1.1.3 Rundholz;
   1.1.4 Waldrestholz (dicke Äste, Baumkronen usw.);
   1.2.1 Chemisch unbehandelte Nebenprodukte und Rückstände aus Industrie-Restholz.

Biocombustibles solides - Classes et spécifications des combustibles - Partie 5: Classes de bois de chauffage (ISO 17225-5:2026)

Le présent document spécifie les classes et spécifications de qualité du combustible pour le bois de chauffage. Il s'applique uniquement au bois de chauffage produit à partir des matières premières suivantes (voir l’ISO 17225-1:2021, Tableau 1):
1.1.1 Arbres entiers sans racines;
1.1.3 Grumes;
1.1.4 Rémanents forestiers (grosses branches, cimes, etc.);
1.2.1 Produits dérivés et sous-produits de l’industrie de transformation du bois sans traitement chimique.

Trdna biogoriva - Specifikacije goriv in razredi - 5. del: Razvrščena drva (ISO/FDIS 17225-5:2026)

General Information

• Status: Published
• Publication Date: 14-Apr-2026
• ICS: 27.190 - Biological sources and alternative sources of energy
• ICS: 75.160.40 - Biofuels
• Technical Committee: CEN/TC 335 - Solid biofuels
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 15-Apr-2026
• Completion Date: 15-Apr-2026
• Ref Project: kSIST FprEN ISO 17225-5:2026 - Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood (ISO/FDIS 17225-5:2026)

Relations

• Replaces: EN ISO 17225-5:2021 - Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood (ISO 17225-5:2021)
• Effective Date: 25-Dec-2024
• Referred By: EN 303-5:2012 - Heating boilers - Part 5: Heating boilers for solid fuels, manually and automatically stoked, nominal heat output of up to 500 kW - Terminology, requirements, testing and marking
• Effective Date: 22-Apr-2026
• Consolidated By: ISO 17225-5:2026 - Solid biofuels — Fuel specifications and classes — Part 5: Graded firewood
• Effective Date: 12-Feb-2026

Overview

EN ISO 17225-5:2026 establishes critical standards for solid biofuels, specifically addressing fuel specifications and classes for graded firewood. Developed by the European Committee for Standardization (CEN) and aligning with ISO methodologies, this document defines quality requirements for firewood intended for use in residential, small commercial, and public building heating appliances. Its scope is limited to firewood derived from specific raw materials: whole trees (without roots), stemwood, logging residues, and chemically untreated by-products from wood processing industries, as referenced in ISO 17225-1.

The aim of EN ISO 17225-5 is to promote clear classification, support efficient solid biofuel trade, ensure consistent fuel quality, and facilitate regulatory communication and compliance across the supply chain.

Key Topics

• Raw Material Classification: Covers only firewood from whole trees (no roots), stemwood, logging residues (such as thick branches and tops), and chemically untreated by-products.
• Fuel Quality Classes: Introduces fuel classes (A1, A2, B) for graded firewood, each with specific characteristics suitable for different applications (such as stoves, fireplaces, and boilers).
• Dimensional Criteria: Specifies firewood dimensions including length and diameter, supporting compatibility with various appliance types.
• Moisture Content: Requires declaration of moisture content, with guidance for both wet and dry basis calculation. Moisture content directly impacts combustion quality and energy output.
• Energy Density: Recommends stating the net calorific value or energy density, enabling fair comparison and efficient energy use.
• Measurement Methods: Details standardized sampling, preparation, and test methods for assessing firewood properties, referencing ISO standards.
• Product Declaration: Emphasizes the importance of accurate product labeling and the supplier's responsibility to ensure reliable information.
• Contamination and Quality Concerns: Provides guidance on identifying contamination sources and assessing firewood for decay or mould.

Applications

The requirements in EN ISO 17225-5 are particularly relevant for:

• Residential Heating: Ensures safe and efficient use of firewood in household wood-burning appliances, such as stoves, fireplaces, cookers, and sauna stoves.
• Small Commercial Buildings: Supports small-scale heating systems with controlled fuel properties for better emission management.
• Public Buildings: Facilitates compliance with air quality and safety standards for solid fuel heating in schools, offices, and similar facilities.
• Biofuel Supply Chain: Enhances transparency and traceability of firewood quality from production to end-user, supporting reliable fuel trade and procurement processes.
• Product Labelling: Enables producers, distributors, and retailers to provide standardized information to consumers, increasing market confidence in firewood for energy use.

Related Standards

Organizations and professionals referencing EN ISO 17225-5 should also be aware of the following related standards for solid biofuels and heating appliances:

• ISO 17225-1:2021 – General requirements for solid biofuels, a primary reference for raw material origin and classification.
• ISO 14780 – Solid biofuels – Sample preparation.
• ISO 16559 – Terminology for solid biofuels.
• ISO 18134-1 / 18134-2 – Methods for determining moisture content.
• ISO 21945 – Simplified sampling for small-scale applications.
• EN 13229, EN 12815, EN 12809, EN 13240, EN 15250, EN 15821, EN 303-5 – European standards for residential and small commercial solid fuel appliances.
• EN 13556 – Nomenclature of timber species in Europe.

These standards ensure harmonization, reliability, and safety across the solid biofuels sector, supporting the sustainable and efficient use of graded firewood worldwide.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 17225-5:2025
01-julij-2025
Trdna biogoriva - Specifikacije goriv in razredi - 5. del: Razvrščena drva (ISO/DIS
17225-5:2025)
Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood (ISO/DIS
17225-5:2025)
Biogene Festbrennstoffe - Brennstoffspezifikationen und ‑klassen - Teil 5:
Klassifizierung von Stückholz (ISO/DIS 17225-5:2025)
Biocombustibles solides - Classes et spécifications des combustibles - Partie 5: Classes
de bois de chauffage (ISO/DIS 17225-5:2025)
Ta slovenski standard je istoveten z: prEN ISO 17225-5
ICS:
75.160.40 Biogoriva Biofuels
oSIST prEN ISO 17225-5:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 17225-5:2025
oSIST prEN ISO 17225-5:2025
DRAFT
International
Standard
ISO/DIS 17225-5
ISO/TC 238
Solid biofuels — Fuel specifications
Secretariat: SIS
and classes —
Voting begins on:
Part 5: 2025-05-14
Graded firewood
Voting terminates on:
2025-08-06
Biocombustibles solides — Classes et spécifications des
combustibles —
Partie 5: Classes de bois de chauffage
ICS: 75.160.10; 27.190; 75.160.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 17225-5:2025(en)
oSIST prEN ISO 17225-5:2025
DRAFT
ISO/DIS 17225-5:2025(en)
International
Standard
ISO/DIS 17225-5
ISO/TC 238
Solid biofuels — Fuel specifications
Secretariat: SIS
and classes —
Voting begins on:
Part 5:
Graded firewood
Voting terminates on:
Biocombustibles solides — Classes et spécifications des
combustibles —
Partie 5: Classes de bois de chauffage
ICS: 75.160.10; 27.190; 75.160.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 17225-5:2025(en)
ii
oSIST prEN ISO 17225-5:2025
ISO/DIS 17225-5:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 Specification of graded firewood . 2
Annex A (informative) Comparison of moisture content as received and dry basis. 5
Annex B (informative) Measurement of firewood . 7
Annex C (informative) Calculation of energy density . 8
Bibliography .10

iii
oSIST prEN ISO 17225-5:2025
ISO/DIS 17225-5:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 238, Solid biofuels.
This third edition cancels and replaces the second edition (ISO 17225-5:2021), which has been technically
revised. The main changes compared to the previous edition are as follows:
— Moisture in Table 1 has been changed.
A list of all parts in the ISO 17225 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
oSIST prEN ISO 17225-5:2025
ISO/DIS 17225-5:2025(en)
Introduction
The objective of the ISO 17225 series is to provide unambiguous and clear classification principles for solid
biofuels; to serve as a tool to enable efficient trading of biofuels; to enable good understanding between seller
and buyer as well as a tool for communication with equipment manufacturers. It also facilitates authority
permission, procedures and reporting.
This document supports the use of graded firewood for residential, small commercial and public buildings
which require classified firewood quality.
The residential, small commercial and public building appliances require higher quality fuel for the following
reasons:
— small-scale equipment does not usually have advanced controls and flue gas cleaning;
— appliances are not generally managed by professional heating engineers;
— appliances are often located in residential and populated districts.
NOTE 1 Firewood produced according to this document can be used in stoves, fireplaces, cookers, room heaters
[1] [2] [3]
and multifired sauna stoves, which are tested according to European standards EN 13229 , EN 12815 , EN 12809 ,
[4] [5] [6] [7]
EN 13240 , EN 15250 and EN 15821 , and boilers systems tested according to EN 303–5 .
NOTE 2 For individual contracts ISO 17225-1 can be used.
Although this document may be obtained separately, it requires a general understanding of the standards
based on and supporting ISO 17225-1. It is recommended to obtain and use ISO 17225-1 in conjunction with
this document.
v
oSIST prEN ISO 17225-5:2025
oSIST prEN ISO 17225-5:2025
DRAFT International Standard ISO/DIS 17225-5:2025(en)
Solid biofuels — Fuel specifications and classes —
Part 5:
Graded firewood
1 Scope
This document determines the fuel quality classes and specifications of graded firewood. This document
covers only firewood produced from the following raw materials (see ISO 17725-1:2021, Table 1):
— 1.1.1 Whole trees without roots;
— 1.1.3 Stem wood;
— 1.1.4 Logging residues (thick branches, tops, etc.);
— 1.2.1 Chemically untreated by-products and residues from wood processing industry.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 17225-1:2021, Solid biofuels — Fuel specifications and classes — Part 1: General requirements
ISO 18134-1, Solid biofuels — Determination of moisture content — Part 1: Reference method
ISO 18134-2, Solid biofuels — Determination of moisture content — Part 2: Simplified method
ISO 21945, Solid biofuels — Simplified sampling method for small scale applications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16559 and the following-apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
firewood
cut and split oven-ready fuelwood used in household wood burning appliances like stoves, fireplaces and
central heating systems
Note 1 to entry: Firewood usually has a uniform length, typically in the range of 15 cm to 100 cm.
Note 2 to entry: Cut-offs from virgin wood can also be used as a firewood.

oSIST prEN ISO 17225-5:2025
ISO/DIS 17225-5:2025(en)
3.2
commercial application
facility that utilizes solid biofuel burning appliances or equipment that have similar fuel requirements as
residential appliances
Note 1 to entry: Commercial applications should not be confused with industrial applications, which can utilize a much
wider array of materials and have vastly different fuel requirements.
4 Symbols and abbreviated terms
The symbols and abbreviated terms used in this document conform with the SI system of units as far a
...