ISO 18400-204:2017

Overview

ISO 18400-204:2017 - "Soil quality - Sampling - Part 204: Guidance on sampling of soil gas" provides international guidance for soil gas sampling in soils and beneath buildings (sub-slab). The standard covers both active sampling (sorbent tubes, filters, air containers, pressurized containers) and passive sampling applied at permanent or temporary monitoring wells and other installations. It gives practical direction on designing a sampling plan, constructing monitoring installations, handling, transport and storage of soil gas samples, and quality assurance for reliable data.

Key topics and requirements

• Sampling methods: Guidance on active and passive soil gas sampling methods, including sorbent tubes, sampling bags, pressurized containers and on-site measurement options.
• Sampling plan: Requirements for developing a sampling plan addressing objectives, initial field screening, locating monitoring wells, horizontal/vertical distribution, timing and frequency, sample volumes and purge procedures.
• Monitoring installation: Construction and preparation of monitoring wells, driven probes, sub-slab ports, gas-monitoring standpipes and associated leak testing.
• Soil gas fundamentals: Basic information on soil gas dynamics, environmental influences, and identification of soil gas sources relevant to boreholes and sub-slab locations.
• Target analytes: Applies to volatile organic compounds (VOCs), inorganic volatile compounds (e.g., mercury, HCN), and permanent gases (CO2, N2, O2, CH4).
• Quality assurance and QA/QC: Chain of custody, field and trip blanks, blind replicates, split samples, contamination and interference considerations, and reporting requirements.
• Sample handling: Procedures for sample identification, packaging, transport and storage to preserve integrity until laboratory analysis.
• Exclusions: Does not cover risk evaluation/characterization, design or verification of protective measures, sampling of atmospheric or indoor gases, measurement of soil gases entering the atmosphere, or radon monitoring.

Applications

• Environmental site investigations and contamination assessments where understanding subsurface gas composition is critical.
• Vapor intrusion studies for sub-slab and indoor air pathway evaluation (sampling guidance, not risk assessment).
• Landfill gas studies, remediation monitoring, and baseline site characterization for redevelopment.
• Field teams performing VOC screening, consultants designing soil gas monitoring networks, and laboratories receiving/handling soil gas samples.

Who should use this standard

• Environmental consultants and field engineers conducting soil gas investigations.
• Remediation project managers and regulators specifying standardized soil gas sampling protocols.
• Laboratories analyzing VOCs and inorganic volatile compounds from gas samples.
• Occupational and building professionals assessing sub-slab gas entry pathways (data collection only).

Related standards

• ISO 18400 series (other parts on soil sampling procedures).
• ISO 10381-7:2005 (superseded by this document).

Keywords: ISO 18400-204:2017, soil gas sampling, VOCs, passive sampling, active sampling, monitoring wells, sub-slab, sampling plan, soil gas dynamics, quality assurance.