ISO 17420-4:2021

Overview

ISO 17420-4:2021 - "Respiratory protective devices - Performance requirements - Part 4: Requirements for supplied breathable gas RPD" defines performance and testing requirements for supplied breathable gas respiratory protective devices (RPD) intended for workplace protection. The standard guides manufacturers, test laboratories, safety engineers and procurement teams on how to classify, evaluate and mark RPD that supply breathable gas (compressed, regenerated or oxygen-enriched) to the wearer to protect against hazardous atmospheres.

Key topics and technical requirements

The standard covers a comprehensive set of performance criteria and test methods, including:

• Classification overview for types and protection classes of supplied breathable gas RPD.
• General requirements such as field of vision, resistance to flame, compatibility with additional equipment, and monitor performance.
• Warning and checking devices: performance expectations for alarms and gas quality/flow checks.
• Protection class determination including procedures like total inward leakage (TIL) testing.
• Validation by practical performance: real-use checks for donning/doffing, communication (hearing and speech), eye irritation, visor fogging, ergonomics and mobility.
• Specific RPD performance for compressed breathable air, regenerated breathable gas and oxygen-enriched gas systems - including work of breathing (WoB), breathing resistance and elastance.
• Capacity and CO concentration limits, plus temperature and humidity requirements for inhaled breathable gas.
• Oxygen content parameters for regenerated and oxygen-enriched systems.
• Hose requirements: flexibility, resistance to kinking and permeation for low/medium/high pressure hoses and varying lengths.
• Compressed gas cylinder and valve assembly requirements, connections and strength tests.
• Optional features and environmental requirements: ambient air bypass, extreme temperature performance, hydration, submersion, electromagnetic compatibility (EMC), and safe use in potentially explosive atmospheres.
• Testing procedures: leak-tightness (positive/negative pressure), high-pressure testing, impact resistance, permeation tests and pre-conditioning.
• Marking and documentation requirements for RPD, components and replacement parts.

Practical applications - who uses ISO 17420-4

• Manufacturers and designers of supplied-air respirators use the standard to design compliant products and to define test protocols.
• Independent test laboratories and certification bodies use it to verify performance and award conformity marks.
• Occupational safety professionals, PPE managers and procurement teams reference the standard when selecting RPD for industrial, firefighting, chemical, mining or confined-space operations.
• Regulators and compliance officers use ISO 17420-4 to align workplace safety rules with internationally accepted performance criteria.

Related standards

ISO 17420-4 is part of the broader ISO 17420 series addressing respiratory protective devices. Users should also consider relevant national PPE standards and other international respirator performance/testing standards when implementing respiratory protection programs.

Keywords: ISO 17420-4, respiratory protective devices, supplied breathable gas RPD, performance requirements, testing, total inward leakage, work of breathing, compressed breathable gas.