The flame ionization detector depends on two gases: ultra-pure hydrogen for the flame and hydrocarbon-free zero air as the oxidant. On-site generation delivers both at the purity your FID demands — no cylinders, no ghost peaks, no compromises.
The FID is the most widely used GC detector in the world. Its sensitivity, baseline stability, and detection limits are directly determined by the purity of the two gases that feed its flame.
Hydrogen burns in air to create a micro-flame at the FID jet tip. Organic compounds passing through the flame are ionized, producing a current proportional to the number of carbon atoms. The hydrogen must be free of organic contaminants to prevent baseline noise.
Zero air provides the oxygen needed to sustain the FID flame. Residual hydrocarbons in the air create a constant background signal that raises the baseline, increases noise, and produces ghost peaks — making THC purity the most critical spec.
The HGA ST series generates both hydrogen and zero air from a single stackable unit — purpose-built for FID applications. One device replaces two cylinder types and supplies carrier gas and FID fuel simultaneously.
Most analysts focus on carrier gas and hydrogen purity, but zero air quality is actually the #1 determinant of FID baseline performance. Here is why: the FID flame burns 300–400 mL/min of air versus only 30–40 mL/min of hydrogen. Any hydrocarbon contamination in the air is amplified 10x by volume.
Cylinder “zero air” is not always zero. Compressed gas suppliers certify zero air at the time of filling, but contamination can occur from cylinder walls, regulators, and tubing. Typical cylinder zero air contains 0.1–1 ppm total hydrocarbons — enough to produce measurable baseline drift and ghost peaks in sensitive FID methods.
Catalytic oxidation technology in LNI Swissgas ZA generators actively destroys residual hydrocarbons by passing ambient air over a heated catalyst bed, converting organic compounds to CO₂ and H₂O. The result is consistently <0.05 ppm THC — every minute, every day, with no batch-to-batch variation.
Run a blank GC-FID analysis with your column disconnected (detector only). If you see baseline drift, periodic spikes, or broad humps, your zero air is the likely culprit. Switch to a ZA generator and repeat the test — the difference is immediate and dramatic.
The FID requires only 30–40 mL/min of hydrogen — a tiny flow rate that means even a small benchtop generator provides months or years of uninterrupted operation from a single unit. The economics are compelling, but the safety and reliability advantages are even more significant.
Safety: A PEM hydrogen generator produces gas on demand from deionized water. The total hydrogen inventory in the system at any moment is typically less than 50 mL — compared to 6,000+ liters at 2,200 psi in a compressed cylinder. Built-in leak detection, pressure limiting, and automatic shut-off make generator hydrogen inherently safer than cylinder hydrogen.
Dual-purpose: If you are already using hydrogen as GC carrier gas (which provides 30–50% faster analysis times than helium), the same generator supplies both your carrier gas and your FID fuel. A single HG PRO at 120–1500 cc/min easily handles carrier + FID for multiple GC instruments.
Consistency: Generator hydrogen purity is constant and documented. Cylinder hydrogen purity can vary between suppliers, between batches, and even within a single cylinder as trace contaminants concentrate as the cylinder empties.
The LNI Swissgas HGA ST series is the only generator that produces both hydrogen and zero air from a single stackable unit. At just 9.5 cm tall, it fits on a benchtop or stacks with other LNI generators to create a complete gas supply station.
How it works: The HGA ST uses PEM electrolysis to generate hydrogen and a separate catalytic oxidation module to produce hydrocarbon-free zero air. Both gases are independently regulated and delivered through separate outlets, so you can set carrier, FID fuel, and combustion air flows independently.
Practical impact: One HGA ST PRO replaces two cylinder types (hydrogen + zero air), eliminates two sets of regulators, two delivery schedules, and two points of failure. For a lab running 1–2 GC-FID instruments, this is the simplest, most cost-effective gas supply solution available.
PRO: PSA drying system, 99.99999% H₂ purity, −75°C dew point. Best for GC-MS carrier + FID fuel dual use. BASIC: Static drying, 99.9999% H₂ purity. Perfect for dedicated FID fuel applications where ultra-high purity carrier gas is not required.
Quick reference for hydrogen and zero air generator selection by FID configuration.
| Configuration | H₂ Source | Air Source | H₂ Flow | Air Flow | Recommended |
|---|---|---|---|---|---|
| Single GC-FID MOST COMMON | HG BASIC | ZA FID Air | 30–40 mL/min | 300–400 mL/min | HG BASIC + ZA FID Air |
| Single GC-FID (all-in-one) | HGA ST BASIC | 30–40 mL/min | 300–400 mL/min | HGA ST BASIC | |
| GC-FID + H₂ carrier | HG PRO | ZA Total | 35–45 mL/min total | 300–400 mL/min | HG PRO + ZA Total |
| GC-FID + H₂ carrier (all-in-one) | HGA ST PRO | 35–45 mL/min total | 300–400 mL/min | HGA ST PRO | |
| Dual GC-FID | HG PRO | ZA Total | 60–80 mL/min | 600–800 mL/min | HG PRO + ZA Total |
| GC with FID + NPD | HG PRO | ZA Total | 35–50 mL/min | 300–400 mL/min | HG PRO + ZA Total + NG EOLO |
| GC with FID + FPD | HG PRO | ZA Total | 60–80 mL/min | 300–500 mL/min | HG PRO + ZA Total |
| 3+ GC-FID (central supply) | HG PRO (high flow) | ZA Rack FID Air | 90–120+ mL/min | 900–1200+ mL/min | HG PRO 1500 + ZA Rack |
Laboratories that switch from cylinder supply to on-site generation for their FID detectors consistently report these benefits.
Catalytic oxidation zero air delivers <0.05 ppm THC every time. No more batch-to-batch variation, no more ghost peaks from contaminated cylinder air. Your FID baseline is as clean as it can get.
A PEM hydrogen generator holds <50 mL of hydrogen at any moment. A cylinder holds 6,000+ liters at 2,200 psi. The safety difference is not incremental — it is transformational.
FID requires both hydrogen and zero air. That means two cylinder types, two rental agreements, two delivery schedules, two regulators. A generator (or combined unit) replaces all of it.
No more interrupted overnight GC-FID runs because hydrogen or air ran out at 2 AM. Your generators run as long as your GC runs.
Cleaner gases = lower baseline noise = lower signal-to-noise ratio = lower detection limits. Some labs report 2–5x improvement in FID detection limits after switching to generators.
No cylinder swaps, no leak testing connections, no regulator replacements, no delivery coordination. Generator maintenance is typically a filter change once or twice per year.
Our hydrogen and zero air generators support FID detectors on every GC platform from every major manufacturer — no modifications needed.
7890, 8890, 8860 GC with FID. Intuvo 9000 with FID. Dual FID configurations. All flow and pressure settings supported.
Nexis GC-2030 with FID-2030. Dual FID/FPD. AOC-6000 Plus autosampler compatibility. Standard flow requirements.
TRACE 1310/1610 GC with FID. AI/AS 1310 autosampler. TriPlus RSH. All FID gas configurations.
Clarus 690 GC with FID. TurboMatrix headspace. Standard H₂ and air flow requirements for all FID applications.
SCION 8300/8500 GC with FID. Environmental and petrochemical FID methods. Dual detector configurations.
Dual FID configurations for simultaneous analysis. Our generators supply both detectors from a single hydrogen and single zero air source.
GC systems running FID alongside NPD, FPD, TCD, or ECD. Generators supply FID gases plus make-up gas for the second detector.
Central gas supply for labs running 3+ GC-FID instruments. HG PRO + ZA Rack FID Air feeds your entire GC suite from one location.
Tell us how many GC-FID instruments you run, whether you also use hydrogen as carrier gas, and your current gas setup. We will recommend the right combination of generators and calculate your ROI.