What Trace Gas Is and Is Not
Trace gas detection is an advanced method used when standard pressure testing confirms a line is leaking but acoustic methods cannot reliably narrow the location to a small enough area for efficient excavation. The gas is introduced into the isolated, pressurized line and allowed to migrate through the leak point and upward through the soil. A detector at the surface identifies where the gas is emerging.
It is not magic. Soil type, moisture content, deck material, pipe depth, leak size, wind conditions, and how the gas was introduced all affect the reading. The result is a clue that narrows the area - not an X on the ground that guarantees one cut will land on the pipe failure.
Hydrogen-Nitrogen Blend vs Helium
Hydrogen-Nitrogen Blend (5% H2 / 95% N2)
- Commonly used in pool and utility leak detection
- Hydrogen is a very small molecule - migrates well through soil and small openings
- Non-flammable at 5% concentration mixed with nitrogen
- Specific detectors required - not interchangeable with helium detectors
- Generally available through industrial gas suppliers in most markets
- LSL uses H2/N2 blend as primary trace gas for pool plumbing work
Helium
- Used in some leak detection industries including HVAC and industrial piping
- Helium is a very small, inert molecule with excellent migration properties
- Requires helium-specific detection equipment
- Can be more expensive and availability varies by market
- LSL also operates helium trace gas capability for specialized applications
- Not as commonly used in pool plumbing detection as H2/N2 blend
What Affects Results Regardless of Gas Type
- Soil type and moisture: Clay, sandy soil, wet conditions, and compacted fill all affect how gas migrates and where it surfaces
- Pipe depth: Deeper leaks require longer migration time and may produce a wider surface signal
- Leak size: A very small leak may not release enough gas to produce a reliable surface reading
- Wind and ventilation: Wind across an open deck area can dilute or displace the emerging gas signal
- Deck material: Solid concrete slabs slow migration differently than paver joints, which can allow faster vertical movement
- Proper line isolation: Gas introduced into the wrong line or a poorly isolated section produces meaningless readings
Leak and Subsurface Locators is one of the only companies in South Florida operating with both H2/N2 blend and helium trace gas systems. Other companies call LSL when they need trace gas capability. This is not the starting point for a new business - it represents years of building toward advanced diagnostic capability after mastering pressure testing, acoustic detection, and field documentation. LBA teaches trace gas as an advanced tool, not a beginner shortcut. Students need pressure testing and line isolation mastered first.
The practical question is not which gas is theoretically better. It is which gas your detector is built for, which your supplier can provide reliably, and which has given you consistent field results in your specific soil and conditions. Either system requires proper setup, correct line isolation, and the patience to read the results accurately before marking a dig location.
Learn Trace Gas as Part of an Advanced Diagnostic System
LBA teaches trace gas in context - after pressure testing fundamentals are solid and line isolation is mastered.
View LBA Courses