ISO 3941:2026

Overview

ISO 3941:2026 - Classification of Fires is an international standard developed by the International Organization for Standardization (ISO). This document classifies fires into distinct categories based on the nature of the fuel involved. Standard fire classifications support the selection and use of appropriate fire protection and firefighting equipment, contribute to effective emergency response planning, and ensure consistency across the fire safety industry. The 2026 edition introduces updates, including the addition of a fire class for lithium-ion batteries, reflecting current risks in modern environments.

Key Topics

Fire Classes Defined by Fuel Type:
ISO 3941:2026 organizes fires into clear categories, each associated with typical fuel examples:

• Class A: Fires involving solid materials such as wood, cloth, paper, rubber, and many plastics, generally producing glowing embers.
• Class B: Fires involving flammable liquids or liquefiable solids.
• Class C: Fires involving flammable gases.
• Class D: Fires involving metals.
• Class F: Fires involving cooking media-specifically oils and fats in kitchen appliances.
• Class L: Fires involving lithium-ion cells and batteries (without elemental lithium).

Hazard Considerations:
Each fire class is accompanied by specific hazards that inform firefighting strategy and equipment selection:

• All classes require attention to the toxicity of combustion products.
• Class A fires may be surface or deep-seated, affecting extinguishing techniques.
• Class B fires demand understanding of fuel containment and liquid properties (e.g., polar vs. non-polar).
• Class C fires pose explosion risks if gas flow cannot be controlled.
• Class D fires are unique to each metal type and require situation-specific responses.
• Class F fires can lead to explosions or dangerous splashing when water is misapplied.
• Class L fires from lithium-ion batteries present added risks such as rapid thermal runaway, explosive gas venting, toxic emissions, projectiles, and the potential for electric shock and re-ignition due to stranded energy.

Applications

ISO 3941:2026 is foundational for diverse fire safety and firefighting applications:

• Equipment Design and Certification: Manufacturers rely on the fire classification system to develop and test fire extinguishers and suppression systems labeled for specific fire classes.
• Fire Safety Training: Provides essential knowledge for fire wardens, emergency responders, and facility managers to identify fire types and select the proper extinguishing method.
• Building and Industrial Safety: Supports regulatory compliance, risk assessment, and emergency planning by defining potential fire scenarios.
• Lithium-ion Battery Risk Management: The new Class L addresses the growing prevalence of battery-powered devices, helping organizations implement targeted controls for electrochemical fires.

Related Standards

Professionals using ISO 3941:2026 may also reference these related international standards to develop comprehensive fire safety strategies:

• ISO 7165: Fire extinguishers - Performance and construction standards
• ISO 14520: Gaseous fire-extinguishing systems - Design and installation
• ISO 21927: Smoke and heat control systems
• IEC 60079: Electrical apparatus for explosive atmospheres

By applying ISO 3941:2026, organizations can ensure accurate classification of fires, select effective firefighting equipment, and strengthen overall fire protection measures. This standard is a key resource for safety compliance across commercial, industrial, and residential environments.