Overview
CEN/TS 18231:2026 is a technical guide published by CEN that explains how to measure the dimensions specified in EN 1335-1:2020+A1:2022 using the chair measuring device (CMD) and test methods of ISO 24496:2021. The document provides clarifications, worked examples and additional guidance to make dimension measurement more precise and less open to interpretation. It is intended to reduce discrepancies between different measurers and to improve repeatability of results.
Key Topics
- Chair setup and CMD placement: Practical guidance on preparing the chair and placing the CMD, including marking useful reference lines (median plane, seat depth line, lumbar zone and seat surface width zone). The CMD should be level and centred; two operators are recommended for positioning.
- Loading and positioning notes: The guide describes how to set the horizontal force loading device (a 40 N horizontal force is applied during CMD lowering) and how to estimate seat depth clearance so the CMD can travel to the backrest without obstruction.
- Adjustment states and measurement sequences: Measurements are taken in the prescribed sequence of EN 1335-1, including procedures with components in middle, minimum and maximum positions. Specific sequences address lumbar support (fmax, fmin, frange), seat height and sitting height (a min/max), seat depth (b min/max), backrest height (h min/max), armrest dimensions (p, q, n, o), and others.
- Measurements without CMD: Guidance is provided for dimensions measured without the CMD such as seat pad width and depth, backrest width and radius, armrest length and width, and clearances between armrest assemblies.
- Record deviations: If a design prevents strictly following the procedure, the document instructs measurers to take measurements as far as possible and to record any deviations in the test report.
Applications
- Test laboratories: Apply consistent measurement methods to reduce inter-laboratory variation.
- Manufacturers and designers: Verify product dimensions against EN 1335-1 requirements using standardized CMD procedures.
- Certification and compliance: Support clear, auditable measurement records for conformity assessment.
Related Standards
- EN 1335-1:2020+A1:2022 - Office furniture - Office work chair - Part 1: Dimensions - Determination of dimensions
- ISO 24496:2021 - Office furniture - Office chairs - Methods for the determination of dimensions
This guide should be used alongside ISO 24496:2021 and EN 1335-1 when performing dimensional measurements to ensure consistent, defensible results.
