Toxic and Hazardous Gas Concentration Testing: Standards, Methods, and Applications

Toxic and hazardous gas concentration testing quantifies the harmful gases released by materials during combustion, thermal decomposition, or normal use, and measures their levels in workplace, indoor, and ambient air. Using internationally recognized methods such as IEC 60754, ISO 5659-2 with FTIR analysis, and the ISO 16000 series, accredited third-party laboratories help manufacturers verify fire safety, environmental compliance, and occupational health performance. This article explains the typical sample types, target analytes, analytical techniques, acceptance criteria, and applications of toxic and hazardous gas concentration testing.

Technical Overview

Toxic and hazardous gas concentration testing determines the identity and quantity of harmful gases evolved when materials decompose or burn, as well as the concentration of such gases in ambient, indoor, and workplace air. Combustion of polymers can generate corrosive halogen acids such as hydrogen chloride, hydrogen bromide, and hydrogen fluoride; asphyxiants such as carbon monoxide, carbon dioxide, and hydrogen cyanide; irritants such as sulfur dioxide, nitrogen oxides, ammonia, and formaldehyde; and a broad spectrum of volatile organic compounds (VOCs). Quantifying these species is essential for fire safety engineering, product certification, occupational hygiene, and environmental compliance.

Test requirements are defined by international and national standards. IEC 60754-1 and IEC 60754-2, adopted in China as the GB/T 17650 series, govern gases evolved from cable materials. EN 45545-2 specifies fire gas analysis requirements for railway applications, combining the ISO 5659-2 smoke chamber with Fourier-transform infrared (FTIR) spectroscopy. ISO 19701 and ISO 19702 define fire-effluent generation and FTIR quantification methods, while the ISO 16000 series, EN 16516, GB/T 18883, and GB 50325 address indoor air and chamber-based emission testing. Accredited third-party laboratories perform these tests to demonstrate compliance and to support research and development programs.

Testing Samples

Cables, Wires, and Cable Materials

Insulation compounds, sheathing compounds, fillers, binding tapes, and finished cable sections are the most frequently tested sample types. Halogen-free and low-smoke zero-halogen (LSZH) formulations are verified for halogen acid content and corrosivity under IEC 60754-1 and IEC 60754-2, together with the related EN 50267 and EN 50305 methods used for railway and other special-duty cables.

Railway and Mass Transit Materials

Interior and exterior components for trains, metros, and trams, including seat cushions and covers, wall and ceiling panels, floor coverings, adhesives, and sealing materials, are tested for fire gas toxicity under EN 45545-2 to satisfy the required hazard levels (HL1 to HL3) for rolling stock applications.

Polymer Compounds, Foams, and Textiles

Thermoplastics, elastomers, polyurethane foams, laminates, coatings, and textile products are evaluated during formulation development to screen flame-retardant systems, halogen content, and smoke toxicity before full-scale production.

Building, Furniture, and Automotive Interior Materials

Paints, adhesives, sealants, wood-based panels, furniture, and vehicle interior trim are tested for formaldehyde and VOC emissions using emission test chambers and cells in accordance with the ISO 16000 series, EN 16516, and Chinese national standards such as GB 50325 and GB/T 18883.

Air and Gas Samples

Workplace air, indoor air, stack emissions, confined-space atmospheres, soil gas, and off-gas from battery thermal runaway events can be sampled directly and analyzed for specific toxic gas concentrations, with results compared against occupational exposure limits such as those in the GBZ 2.1 standard.

Testing Items

Common target analytes and measured parameters include:

• Hydrogen chloride (HCl), hydrogen bromide (HBr), and hydrogen fluoride (HF), the halogen acids released by halogenated polymers and flame retardants
• Carbon monoxide (CO) and carbon dioxide (CO2), the primary asphyxiant fire gases
• Hydrogen cyanide (HCN), generated by nitrogen-containing polymers such as polyurethane and polyamide
• Nitrogen oxides (NO and NO2), sulfur dioxide (SO2), and hydrogen sulfide (H2S)
• Ammonia (NH3) and ozone (O3) where process-relevant
• Formaldehyde and other low-molecular-weight aldehydes
• Total volatile organic compounds (TVOC) and individual VOCs including benzene, toluene, ethylbenzene, xylenes, and styrene
• Acidity and corrosivity parameters, namely the pH and conductivity of the gas absorption solution per IEC 60754-2
• The Conventional Index of Toxicity (CIT) calculated from CO2, CO, HF, HBr, HCl, HCN, NO2, and SO2 concentrations per EN 45545-2
• Fractional effective dose (FED) and fractional effective concentration (FEC) indices used in fire hazard engineering assessment

Testing Methods

Fire-Effluent Generation Methods

Material-based tests decompose or combust a conditioned specimen under controlled conditions and collect the evolved gases for analysis:

• IEC 60754-1: the material is heated in an air stream within a tube furnace, halogen acids are absorbed in aqueous solution, and the halide content is quantified by titration or ion chromatography. Halogen acid content below 5 mg/g (0.5%) is typically required to claim halogen-free status.
• IEC 60754-2: gases evolved at approximately 935 degrees Celsius are absorbed in water, and the pH and conductivity of the solution are measured; typical acceptance criteria are pH not less than 4.3 and conductivity not greater than 10 microsiemens per millimeter for low-corrosivity materials.
• ISO 5659-2 smoke chamber combined with FTIR analysis: specimens are exposed at 25 kW/m2 and 50 kW/m2 irradiance under flaming and non-flaming conditions, and gas concentrations are recorded continuously as required by EN 45545-2 for CIT calculation.
• ISO 19701 steady-state tube furnace with ISO 19702 FTIR analysis: fire effluents are generated under controlled ventilation conditions ranging from well-ventilated to under-ventilated combustion for full toxicity characterization.
• NF X 70-100 tube furnace: pyrolysis and combustion at controlled temperatures with gas trapping, widely referenced in European railway material qualification programs.
• ISO 5660-1 and ASTM E1354 cone calorimeter: heat release rate measurement that can be coupled with gas analyzers for CO, CO2, and smoke yield determination.

Analytical Instrumentation

• Ion chromatography for HCl, HBr, HF, sulfate, nitrate, and other absorbed ionic species
• FTIR spectroscopy for simultaneous multi-gas quantification of CO, CO2, HCl, HBr, HF, HCN, SO2, NO2, and light hydrocarbons
• Gas chromatography with mass spectrometry (GC-MS) and GC-FID for VOCs and hydrocarbon speciation
• High-performance liquid chromatography (HPLC) and spectrophotometry with DNPH or acetylacetone derivatization for formaldehyde and aldehydes
• Chemiluminescence analyzers for NOx, non-dispersive infrared (NDIR) analyzers for CO and CO2, ultraviolet fluorescence analyzers for SO2, and photoionization detectors (PID) for TVOC screening
• Electrochemical sensors and colorimetric detector tubes for on-site screening and confined-space entry verification

Air Monitoring and Emission Testing

Air-based programs combine validated sampling strategies with laboratory analysis. Sorbent tubes followed by thermal desorption in accordance with ISO 16017, evacuated canister sampling with GC-MS analysis, impinger absorption, and passive diffusive samplers are used for time-weighted and real-time exposure assessment. Building and furniture products are evaluated in emission test chambers and emission cells per ISO 16000-9 and ISO 16000-6, with reference to EN 16516, GB/T 18883, and GB 50325 limit values, while workplace measurements follow GBZ/T 300 series analytical methods.

Applications

• Certification of halogen-free, low-smoke cables for rail transit, tunnels, ships, airports, data centers, and high-rise buildings
• Rolling stock material qualification and fire safety assessment to the hazard levels defined in EN 45545-2
• Green building compliance and indoor air quality verification against formaldehyde and VOC emission limits
• Occupational health surveillance, permit-to-work programs, and confined-space entry risk management
• Research into polymer combustion chemistry, flame-retardant development, and battery thermal runaway gas characterization
• Quality control of incoming materials and formulation change management in wire, cable, and component manufacturing

FAQ

What is the purpose of toxic and hazardous gas concentration testing?

It quantifies gases that threaten life safety, corrode electronic equipment and structures, or degrade indoor air quality. The resulting data support product certification, fire risk assessment, exposure control, and regulatory compliance.

Which gases are typically measured?

The most common analytes are HCl, HBr, HF, HCN, CO, CO2, SO2, NOx, NH3, formaldehyde, and VOCs, together with derived indices such as CIT, FED, and FEC, and solution-based parameters such as pH and conductivity.

What sample preparation is required for IEC 60754 testing?

A few grams of polymeric material are required, granulated to approximately 1 mm or smaller. Finished cables are stripped so that insulation and sheath fractions are tested separately, and specimens are conditioned in a standard atmosphere before testing.

What are the typical acceptance criteria?

Halogen acid content below 0.5% per IEC 60754-1, pH not less than 4.3 and conductivity not greater than 10 microsiemens per millimeter per IEC 60754-2, CIT limits according to the applicable requirement set and hazard level in EN 45545-2, and workplace air results compared against GBZ 2.1 occupational exposure limits.

How long does a testing program take?

Individual combustion runs are short, but a complete program including conditioning, multiple exposure conditions, duplicate runs, instrument calibration, and reporting typically requires one to three weeks depending on the scope.

Can both materials and air samples be tested?

Yes. Accredited third-party laboratories commonly offer material fire-effluent testing, chamber emission testing, and field air monitoring under a single scope, allowing consistent comparison of laboratory and site data.