ISO 19703:2018

Overview - ISO 19703:2018 (Generation and analysis of toxic gases in fire)

ISO 19703:2018 defines methods, equations and sample calculations for quantifying toxic gas and smoke yields produced in experimental fires. The standard focuses on converting time‑resolved experimental measurements into species yields (mass per mass of fuel consumed) and on characterizing the combustion conditions that produced them using equivalence ratio and combustion efficiency. It is intended for fire researchers and test laboratories working with bench‑scale, reduced‑scale and full‑scale fire tests where time‑resolved data are available.

Key topics and technical requirements

• Definitions, symbols and units: consistent terminology for gas/particle mass concentration and related quantities (referenced to ISO 13943).
• Input data and data handling: requirements for recording test specimen composition, net heat of combustion, apparatus and set‑up, data acquisition, uncertainty treatment, significant figures and rounding.
• Calculation of species yields: methods to compute measured yields from gas concentration data and to estimate notional yields from elemental composition or empirical formula.
• Elemental mass recovery and stoichiometry: procedures to assess recovery of key elements and to calculate stoichiometric oxygen‑to‑fuel mass ratio (from chemical equations, net heat of combustion or carbon content).
• Smoke yields: approaches for mass‑based smoke particulate yields and for light‑obscuration based yields, and relationships between mass measurements and optical obscuration.
• Equivalence ratio (ϕ): derivations and calculation methods for flow‑through steady‑state systems, calorimeters, closed chambers and room fire tests.
• Combustion efficiency: multiple metrics including heat release efficiency, oxygen‑consumption based methods (oxygen depletion and oxygen‑in‑products) and oxides‑of‑carbon methods.
• Sample calculations: worked examples to produce instantaneous or averaged values from time‑resolved test data.

Practical applications and who uses this standard

ISO 19703 is used by:

• Fire researchers and laboratories to record and report standardized yields of toxic gases and smoke from experimental fires.
• Fire safety engineers and modelers who need yield data for fire hazard assessments and input to dispersion or evacuation models.
• Product manufacturers and test houses comparing bench‑scale apparatus results with expected full‑scale behaviour (e.g., to validate bench tests).
• Regulatory and standards bodies for harmonized reporting of combustion products (note: the standard does not provide toxicological interpretation or apparatus operating procedures).

Practical benefits include reproducible yield calculations, clearer characterization of combustion regimes (equivalence ratio, efficiency), and better comparability between test setups and fire models.

Related standards

• ISO 13943 - Fire safety: vocabulary (terminology used)
• ISO 13571 - Guidance on assessment of human exposure and time to incapacitation
• ISO 19706 - Guidance on fire conditions and bench‑scale to full‑scale comparability

Keywords: ISO 19703:2018, toxic gases in fire, species yields, equivalence ratio, combustion efficiency, fire testing, smoke yields, oxygen consumption, experimental fires.