Why Your H₂S Analyzer Keeps Failing

Christian Kurz
Jul 7
3 min read

Avoid costly shutdowns, false readings, and safety risks with these insights.

Hydrogen sulfide (H₂S) analyzers play a critical role in oil and gas operations, particularly in sour gas applications. Yet many operators face recurring issues with analyzer reliability—ranging from inaccurate readings to total equipment failure. These problems aren't just frustrating—they can lead to compliance violations, safety risks, and costly downtime.

So why do H₂S analyzers fail? Here are the top 5 causes and how to fix them.

1. Inadequate Sample Conditioning

Your analyzer is only as good as the sample it receives. If you’re feeding it a wet, dirty, or inconsistent stream, failure is inevitable.

Common problems:

Liquid carryover
Particulate contamination
Pressure or flow fluctuations Fix: Always create phase diagrams to design sampling systems so that temperature and pressure remain the gas phase region—so H₂S or O₂ doesn’t drop out as liquid. Always install your sample probe in the middle ⅓ of the process pipe and if necessary install all of the proper sample conditioning system components like: coalescing filters, pressure regulators, water membrane separators and temperature control to keep a clean, dry, and stable gas. This will ensure long sensor life and optimal analyzer performance.

2. Poor Calibration Practices

Skipping regular calibration—or doing it wrong—leads to drift, false readings, and failed audits.

Common mistakes:

Using expired or cheap span gas
Not zeroing before span calibration
Calibrating too infrequently

Fix: Set a strict calibration schedule. Use accurate calibration gas and follow the analyzer manufacturer’s steps precisely for accurate calibration. Pro Tip: When calibrating H₂S sensors, always check the calibration gas certificate—using gas with a ±5% tolerance can introduce more error than your sensor’s resolution. For the most accurate results, choose calibration gas with ±2% (or better) certified accuracy, especially when tight tolerances matter.

3. Environmental Extremes

H₂S analyzers are sensitive to temperature swings, vibration, and moisture—conditions common in the field.

Resulting failures:

Sensor degradation
Electronic faults
Premature component wear

Fix: Use analyzer shelters or climate-controlled enclosures. Mount analyzers away from vibration sources and extreme elements. Choose industrial-grade and/or heated enclosures if exposed to the open.

4. Wrong Analyzer Type for the Application

Not all H₂S analyzers are built the same. Optical, electrochemical, and TDLAS sensors each have different strengths and limitations.

Mismatch symptoms:

Slow response time
Short sensor life
Incompatibility with gas composition

Fix: Ensure your analyzer matches your gas composition, pressure range, and required response time. Work with an ISG instrumentation consultant if you're unsure.

5. Lack of Preventive Maintenance

A “set it and forget it” approach leads to system neglect—and eventual failure.

Neglected tasks include:

Filter changes
Leak checks
Sensor replacements

Fix: Implement a preventive maintenance checklist and SCADA-based maintenance alerts. Track component life and condition in real time.

Bonus Tip: Integrate with SCADA for Real-Time Monitoring

Modern SCADA platforms allow you to:

Detect sensor drift before it becomes critical
Set alarms for abnormal readings or calibration overdue
View historical trends to predict failure patterns

This predictive oversight can prevent most failures before they occur—and keep your H₂S system compliant, accurate, and safe.

Final Thoughts

If your H₂S analyzer keeps failing, it’s not just bad luck—it’s a sign something in your setup or process needs attention. From sample conditioning to SCADA integration, addressing the root causes can turn a high-maintenance device into a trusted asset.