ISO 21925-2-2021 PDF

Full title and description

ISO 21925-2:2021 — Fire resistance tests — Fire dampers for air distribution systems — Part 2: Intumescent dampers. This International Standard specifies a furnace test method and associated requirements to determine the fire resistance performance of intumescent (non‑mechanical) fire dampers installed in ducted air distribution systems and to evaluate their ability to prevent the spread of fire and hot gases (and associated smoke) between fire compartments.

Abstract

ISO 21925-2:2021 defines the test principles, apparatus, installation and measurement procedures for assessing intumescent fire dampers. The standard is intended for dampers expected to be classified as EI dampers (insulation and integrity). It sets requirements for furnace conditions, leakage measurement, connecting duct construction, specimen installation, operational checks and reporting. The document excludes devices used only for smoke control, air‑transfer only devices and certain suspended‑ceiling applications where separate evaluation is required.

General information

• Status: Published (International Standard).
• Publication date: 25 June 2021.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 13.220.50 — Fire‑resistance of building materials and elements.
• Edition / version: 1st edition (2021).
• Number of pages: 44.

Scope

The standard specifies a fire resistance test method for intumescent fire dampers used in air distribution (ducted) systems. It covers test apparatus and instrumentation, specimen construction and installation, connecting‑duct requirements, leakage measurement under a specified pressure differential, operational/durability checks and classification/reporting of results. ISO 21925-2:2021 applies to intumescent dampers intended to achieve an EI classification; because intumescent dampers lack mechanical closure they cannot, by themselves, meet the “S” (ambient leakage) classification. The standard is not intended for dampers solely used for smoke control, for devices used only for low‑pressure air transfer through doors or walls without ducts, or for some suspended‑ceiling installations where the ceiling assembly must be evaluated separately.

Key topics and requirements

• Test principles and furnace conditions consistent with standard fire exposure (reference to ISO furnace/time–temperature methods).
• Leakage/tightness measurement by direct flow measurement across the closed damper while maintaining a constant pressure differential (typically 300 Pa unless otherwise required).
• Requirements for test apparatus: condensing devices ahead of flow meters, exhaust and pressure control, and instrumentation tolerances.
• Connecting‑duct construction and sizing rules (welded steel duct, specified thickness and length related to damper size).
• Specimen installation rules for multiple mounting options (in‑wall, in‑floor, mounted on face of construction, remote mounting in ductwork) and orientation considerations.
• Size and sampling guidance: largest damper tested can be extended to smaller sizes under stated conditions; guidance on number of tests for different installation cases.
• Operational and durability checks (opening/closing cycles, conditioning) and annexed guidance on durability and reaction‑to‑fire for intumescent materials.
• Classification and reporting requirements, and instructions for stating the direct field of application of the test results.
• Explicit exclusions and limitations (smoke‑control only devices, certain suspended‑ceiling installations, air‑transfer only applications).

Typical use and users

ISO 21925-2:2021 is used by fire‑test laboratories, fire damper manufacturers, product certification bodies, HVAC and fire‑safety engineers, building code and compliance authorities, and specifiers. Typical applications include type‑testing of intumescent dampers for product certification, performance verification for product listings, and technical reference when specifying dampers for ducted HVAC systems in buildings subject to fire‑resistance requirements.

Related standards

Related and commonly referenced documents include ISO 21925-1 (Part 1: Mechanical dampers), earlier ISO 10294 series (withdrawn/replaced by the ISO 21925 series), ISO 834-1 (fire resistance furnace/time–temperature curve and apparatus references used in fire tests), ISO 5167 (flow measurement guidance used for leakage measurement), and regional product/test standards and EN standards for fire‑resisting installations (used in conjunction with ISO methods where national or regional rules apply). The standard was developed by ISO/TC 92/SC 2 (fire containment).

Keywords

ISO 21925-2:2021; fire resistance tests; fire dampers; intumescent dampers; EI classification; leakage testing; air distribution systems; furnace test; duct testing; fire containment; test apparatus; durability.

FAQ

Q: What is this standard?

A: ISO 21925-2:2021 is an International Standard that specifies a fire‑resistance test method and related requirements for intumescent fire dampers used in ducted air distribution systems.

Q: What does it cover?

A: It covers test principles, furnace and apparatus requirements, connecting‑duct and specimen installation rules, leakage/tightness measurement procedures, operational and durability checks, criteria for classification (EI performance), and reporting and application guidance. It excludes dampers used only for smoke control, air‑transfer‑only devices and certain suspended‑ceiling arrangements.

Q: Who typically uses it?

A: Fire test laboratories, damper manufacturers and designers, certification and conformity assessment bodies, HVAC engineers, and building officials use this standard for type testing, certification, specification and regulatory compliance.

Q: Is it current or superseded?

A: ISO 21925-2:2021 is the current (1st) edition published on 25 June 2021. Users should check for any later amendments or national adoptions if precise regulatory compliance is required.

Q: Is it part of a series?

A: Yes — it is Part 2 of the ISO 21925 series for fire dampers for air distribution systems. Part 1 covers mechanical dampers (ISO 21925-1:2018); earlier ISO 10294 parts were superseded by the ISO 21925 series.

Q: What are the key keywords?

A: Fire dampers, intumescent dampers, fire resistance test, EI classification, leakage measurement, duct testing, ISO 21925-2, HVAC fire protection, test apparatus, durability.