Overview
ISO 16976-4:2023 - Respiratory protective devices - Human factors - Part 4: Work of breathing and breathing resistance: physiologically based limits provides a physiological framework and calculation methods to assess how much additional respiratory load a person tolerates when wearing a respiratory protective device (RPD). The standard describes how to calculate the work performed by respiratory muscles with and without external impediments imposed by RPDs (all types except diving equipment) and supplies values and criteria that can be used to judge RPD acceptability.
Key technical topics and requirements
- Definitions and symbols: common terms (WoB, VT, VC, FRC/ERV, elastance/compliance) and units (Joules, kPa, litres BTPS).
- Pressure and volume behavior: analysis of pressure–volume changes during breathing both without an RPD and with RPD-imposed flow resistance and static pressure.
- Work of breathing (WoB):
- Distinction between physiological and physical work, including static and elastic components.
- Methods for calculating inspiratory, expiratory and total WoB, and normalization (WoB/VT).
- Procedures to compute the wearer’s WoB while using an RPD and the WoB contribution attributable to the RPD itself.
- Breathing resistance: characterization of flow resistance effects and how these add to natural airway resistance.
- Physiologically acceptable limits: presentation of physiologically based WoB limits and values to assess the acceptability of RPD designs.
- Other respiratory loads: treatment of static pressure loads, elastic loads and combined effects, and guidance on how loads accumulate.
- Scope and exclusions: applies to all RPDs except diving equipment.
Practical applications
- RPD design and engineering - use the WoB calculations to optimize filter/media resistance, valve design, and dead space to minimize wearer burden.
- Laboratory testing and certification - incorporate physiologically based WoB limits into performance protocols and acceptance criteria.
- Occupational health and safety - assess whether a given RPD is suitable for specific work rates, tasks or populations based on tolerable respiratory loads.
- Human factors and ergonomics - evaluate fit, breathing comfort and sustained usability for workers, first responders and healthcare personnel.
- Regulatory guidance and procurement - inform specifications for PPE selection, procurement, and compliance checks.
Who should use this standard
- PPE and respirator manufacturers, test laboratories, accreditation bodies
- Occupational hygienists, safety engineers and ergonomists
- Standards developers and policy makers involved in respiratory protection
Related standards
- ISO 16972 - Vocabulary and graphical symbols for respiratory protective devices
- Other parts of the ISO 16976 series covering human factors for RPDs
Keywords: ISO 16976-4:2023, work of breathing, breathing resistance, respiratory protective device, RPD, physiologically based limits, respiratory muscle work, PPE testing, occupational safety.
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