# Soil Gas Sampling: How to Choose Probes, Depth and Leak Tests in Canada

> Active vs passive soil gas sampling, probe depth, equilibration and leak testing per Health Canada, CCME and DTSC, plus the AMS gas vapor probe line ERE carries.

- **URL:** https://www.ereinc.com/blogs/field-notes/soil-gas-sampling-how-to-choose-probes-depth-and-leak-tests-in-canada

Soil gas sampling means pulling vapour out of the pore space of the soil, through a small probe, so a lab or a field screening instrument can tell you what volatile contaminants are present and how much. It is the standard way to check whether hydrocarbon or solvent vapours could be moving toward a building. This guide covers active and passive methods, how deep to sample, how long to wait, how to leak-test, and which probe hardware ERE carries from AMS.

**Key takeaways**
- **Active sampling pumps a measured volume out of the ground;** passive sampling leaves an absorbent in the soil for days or weeks. Active is the faster route when volatile organic compounds are the concern.
- **Depth is set by guidance, not by the probe.** Health Canada and CCME state a minimum of 1 m below the foundation slab for building-related work.
- **A probe is not ready the moment it is driven.** CCME equilibration times run from 20 minutes for driven probes to one week for air-rotary holes.
- **Leak testing is part of the sample,** not an extra. A sample drawn through a leaking seal reads low and proves nothing.

**In this guide**
- [What is soil gas sampling and when do you need it?](#what)
- [Should you use active or passive soil gas sampling?](#method)
- [How deep should a soil gas probe go?](#depth)
- [How long do you wait after installing a probe?](#wait)
- [How do you purge and leak-test a probe?](#purge)
- [Which probe design suits which job?](#designs)
- [What soil gas sampling equipment does ERE carry?](#ere)
- [How do you plan a soil gas sampling event, step by step?](#steps)
- [Frequently Asked Questions](#faq)

## What Is Soil Gas Sampling and When Do You Need It?

Soil gas sampling collects the vapour that sits in the soil pores near a contamination source or a building, then measures it. Consultants use it on hydrocarbon spill sites, leaking underground storage tanks and pipelines, landfills, and solvent sites, and as a screening step for vapour intrusion into buildings. It sits alongside groundwater and soil sampling, not in place of them, because vapour concentrations depend on soil moisture, permeability and depth as well as on the source.

It also answers a different question from a soil sample. A soil sample tells you what is in the soil; a soil gas sample tells you what is leaving it as vapour. For volatile organic compounds in soil itself, a sealed coring device such as the [En Core® sampler](/products/en-core%C2%AE-samplers) (built for SW-846 Method 5035 work) is the tool; for the vapour phase, you need a gas probe.

## Should You Use Active or Passive Soil Gas Sampling?

Use active sampling when volatile organic compounds are the main concern and you need data quickly; use passive sampling where power is unavailable or you need a long, unattended integration. The [US EPA CLU-IN vapour intrusion site investigation tools page](https://clu-in.org/issues/default2.focus/sec/Vapor_Intrusion/cat/Site_Investigation_Tools/) defines the two:
- **Active:** soil gas is collected by pumping a volume from the target zone, and samples can be analyzed immediately. It supports rapid assessment, and samples can come from temporary or permanent probes installed by augered borings or direct push.
- **Passive:** absorbent materials are left in the ground for days or weeks and collect vapours through the ambient flow of soil gas. Samplers can go where there is no power and sit unattended.

The hardware in this guide is for active sampling: a probe in the ground, tubing to the surface, and a pump, canister or field instrument on the other end.

## How Deep Should a Soil Gas Probe Go?

For building-related work, the minimum is 1 m below the foundation slab. The [Contaminated Sites Approved Professional Society of BC guidance on the soil vapour to air pathway](https://csapsociety.bc.ca/wp-content/uploads/CSAP-Vapour-Guidance-Update-31August_20.pdf) reports that Health Canada (2010) and CCME (2016) set the minimum at 1 m below the slab, compared with 1.5 m (5 ft) in US guidance.

Where a shallow water table prevents that, the same document notes that CCME (2016) accepts valid samples from as shallow as 0.5 m with precautions: a plastic ground sheet and a probe seal verified by a leak test. It also warns that shallow external samples can be unrepresentative of conditions under a building. Treat depth as a project decision your consultant documents, not a default.

## How Long Do You Wait After Installing a Probe?

Driving a probe disturbs the soil, so wait for the subsurface to settle before you sample. The CSAP document summarises CCME (2016) equilibration times:

 | How the probe went in | Minimum wait (CCME 2016, as summarised by CSAP)

 | Driven probe, or direct-push rods left in the ground | 20 minutes

 | Small-diameter direct-push hole | One day

 | Auger or rotosonic hole with no air or water used | Two days

 | Air-rotary or hydrovac hole (develop first) | One week

The same document describes the California DTSC (2015) protocol, which asks for at least two hours for direct-push probes and 48 hours for hollow-stem or hand-auger probes. The two sets of figures differ, so confirm which one your regulator or project plan follows before you write the schedule.

## How Do You Purge and Leak-Test a Probe?

Purge the dead volume first, then confirm the seal holds with a tracer. The CSAP summary of the DTSC (2015) protocol lists these controls:
- **Shut-in test** before purging or sampling, with a measured vacuum of at least 100 in (39.7 cm) of water column and the sample canister attached and valve closed.
- **Leak test** at every probe each time a sample is collected, using a liquid tracer such as difluoroethane or n-propanol, or a gas such as helium or sulphur hexafluoride.
- **Flow rate** of 100 to 200 mL/min for purging and sampling, with vacuum kept below 100 in (39.7 cm) of water column.
- **Purge volume** of three borehole volumes.

Acceptable analysis methods named in the same source include canisters (US EPA Methods TO-14 and TO-15) and active sorbent samplers (TO-17). Those canisters, tracers and the laboratory come from your lab or consultant; ERE's records for these products list the probe hardware and tubing, not canisters or tracer gas.

## Which Probe Design Suits Which Job?

Match the probe to the soil and the number of depths you need. AMS builds the gas vapor probe (GVP) line in three working configurations:

 | Configuration | How it works | Suits

 | "Original" probe (manual drive) | Base section with soil gas access holes, a liner rod that keeps soil out while driving, extension rods and a cross handle | Shallow preliminary sampling in soft, penetrable soil

 | Dedicated tip | Stainless steel tip left in the ground, with a PTFE (fluoropolymer) umbrella and an optional #50 mesh screen; inlet holes slightly recessed and protected by the drive tubes | Repeat sampling at a fixed depth through a stable, clog-resistant point

 | Retract-A-Tip | Hardened stainless tip that opens when the extensions are pulled back a few inches, then can be driven deeper and reopened | Survey work: several depths from one probe string

The Retract-A-Tip record notes it can also be used with a PID or FID by connecting a water trap to the sample delivery tube and applying vacuum to the other side of the trap, which gives a direct reading of contaminant level. If you are choosing the screening instrument, see our [photoionization detector buyer's guide](/blogs/field-notes/photoionization-detectors-pid-a-buyers-guide-for-canada).

## What Soil Gas Sampling Equipment Does ERE Carry?

ERE carries the AMS gas vapor probe line in our [Soil Gas Sampling collection](/collections/soil-gas-sampling). From the product records:
- The ["Original" Gas Vapor Probe](/products/original-gas-vapor-probe) kit includes the GVP base with liner rod and couplings, a hammer adapter, a 914.4 mm (3 ft) extension with liner rod, a barbed adapter and a cross handle; kit weight is listed as 13.75 lb. It is a manual-drive system for shallow sampling in soft soil, with 3/16 in. ID tubing.
- [Dedicated Gas Vapor Tips](/products/dedicated-gas-vapor-tips) are sold as a stainless tip and umbrella, a fluoropolymer umbrella and a #50 mesh screen, for monitoring hydrocarbon spills, tank and pipe leakage, landfills and hazardous waste sites.
- [Retract-A-Tip](/products/retract-a-tip) is a 300 series stainless body with a 400 series stainless tip and #50 mesh screen, for discrete samples at multiple depths.
- [Gas Vapor Probe Kits with dedicated tips](/products/gas-vapor-probe-kits-dedicated-tips) and [kits with dedicated tips and Retract-A-Tip](/products/gas-vapor-probe-kits-with-dedicated-tips-and-retract-a-tip) bundle drive extensions, a slide hammer, a hand pump, a 250 ft roll of 3/16 in. fluoropolymer tubing and a carrying case. Heavy-duty versions add flighted augers, and some variants include a Dewalt D25600K or Bosch 11245EVS hammer drill. Listed kit weights run from 115 to 178 lb, so plan freight.

Models, options and availability change, so request a quote for current configurations. We do not list prices on the website.

## How Do You Plan a Soil Gas Sampling Event, Step by Step?
- **Define the question.** Screening for a spill, delineating a plume, or building-related vapour intrusion each set different depths and detection limits.
- **Confirm the protocol.** Check which guidance your regulator follows for depth, equilibration and leak testing.
- **Choose the probe.** Original for shallow soft soil, dedicated tips for repeat sampling, Retract-A-Tip for several depths.
- **Choose the drive method.** Slide hammer or an electric rotary hammer with the right adapter, depending on soil and depth.
- **Install and wait.** Drive to depth, seal the surface, and hold for the equilibration time.
- **Shut-in test, purge, leak test, sample.** Collect into a canister or sorbent tube, or read with a field instrument, and send samples to an accredited lab.

For the wider site investigation, the [Phase II ESA equipment checklist](/blogs/field-notes/phase-ii-environmental-site-assessment-esa-equipment-checklist-for-canadian-consultants) puts soil gas work in context, and the [environmental sampling equipment guide](/blogs/field-notes/environmental-sampling-equipment-guide-for-canada-ere) covers the other media.

**Need soil gas probes or a complete GVP kit?**

ERE has supplied environmental consultants across Canada since 1994. Tell us the soil, depth and drive method and we will configure the kit.

[**Request a Quote**](/pages/request-a-quote) · [Soil Gas Sampling collection](/collections/soil-gas-sampling)

## Frequently Asked Questions

## What is the difference between soil gas and soil vapour sampling?

None in practice. Soil gas, soil vapour and soil vapor all describe sampling the gas in soil pores. Canadian guidance tends to spell it vapour; US sources spell it vapor.

## How deep should a soil gas sample be taken?

For building-related work, Health Canada and CCME state a minimum of 1 m below the foundation slab. CCME accepts samples as shallow as 0.5 m with a ground sheet and a verified probe seal.

## How long should a soil gas probe sit before sampling?

CCME times range from 20 minutes for driven probes to one week for air-rotary holes. California DTSC asks for at least two hours on direct-push probes. Follow the protocol your regulator uses.

## Why leak-test a soil gas probe?

A leak lets ambient air dilute the sample, so results read low. The DTSC protocol calls for a tracer leak test every time a sample is collected, using a liquid such as n-propanol or a gas such as helium.

## Can one probe sample several depths?

Yes, with a retractable tip. The AMS Retract-A-Tip opens when the extensions are pulled back, can be driven deeper and reopened, and takes a discrete sample at each depth.

## Related articles
- [Phase II ESA Equipment Checklist for Canadian Consultants](/blogs/field-notes/phase-ii-environmental-site-assessment-esa-equipment-checklist-for-canadian-consultants)
- [Photoionization Detectors (PID): A Buyer's Guide for Canada](/blogs/field-notes/photoionization-detectors-pid-a-buyers-guide-for-canada)
- [Soil Vapor Extraction Systems: How They Work](/blogs/field-notes/soil-vapor-extraction-systems-how-they-work-and-when-you-need-one)
- [Tedlar Gas Sampling Bags: Buyer's Guide for Canada](/blogs/field-notes/tedlar-gas-sampling-bags-buyers-guide-for-canada)
- [Environmental Sampling Equipment Guide for Canada](/blogs/field-notes/environmental-sampling-equipment-guide-for-canada-ere)

*Lire en français : [Échantillonnage des gaz du sol : sondes, profondeur et essais d'étanchéité au Canada](/blogs/perspectives-securite/echantillonnage-des-gaz-du-sol-sondes-profondeur-et-essais-detancheite-au-canada)*