A combustible gas detector that shows non-zero readings in clean air—or displays inaccurate concentrations when gas is present—is not just an annoyance. It’s a safety hazard.
False readings can lead to:
Missed alarms during real gas leaks
Unnecessary evacuations and production disruptions
Lost trust in your safety systems
Compliance failures during inspections
This comprehensive guide covers the two most common accuracy problems: zero drift and excessive display error. For each, we explain the root causes and provide step-by-step solutions.
| Problem | Common Causes | Quick Action |
|---|---|---|
| Non-zero reading in clean air | Power supply method, sensor contamination, high gas exposure | Check power supply; clean sensor; recalibrate |
| Readings too low | Aging sensor, wrong calibration gas, span drift | Verify gas type; recalibrate; consider sensor replacement |
| Readings too high | Sensor contamination, electrical interference | Clean sensor; eliminate interference sources |
| Readings unstable / fluctuating | Loose connections, environmental factors, sensor end-of-life | Check wiring; stabilize environment; replace sensor |
Zero drift occurs when a gas detector displays a positive reading even though no combustible gas is present in the environment. This can be caused by several factors.
The Problem:
Some combustible gas detectors use a constant voltage bridge circuit power supply. These designs are inherently susceptible to zero drift caused by temperature fluctuations. As ambient temperature changes, the bridge circuit becomes unbalanced, producing a false signal.
Technical Explanation:
In a constant voltage system, temperature changes alter the resistance of the sensing element differently than the reference element. This imbalance appears as a non-zero output—even with no gas present.
✅ Solution:
| Solution | Description | Difficulty |
|---|---|---|
| Preferred | Replace or upgrade to a detector using constant current bridge circuit power supply. This design compensates for temperature effects automatically. | Moderate (may require new unit) |
| Interim | Use the zero adjustment circuit on the control unit to recalibrate the output to zero. Note: This addresses the symptom, not the cause. | Easy |
Best Practice: When purchasing new detectors, specify constant current bridge circuit designs for applications where temperature varies significantly.
The Problem:
If a detector is exposed to a gas concentration significantly above its measurement range, the sensing element can suffer irreversible changes. The resistance value of the sensing element may be permanently altered, causing the bridge circuit output to remain unbalanced even after the gas clears.
✅ Solution:
| Step | Action |
|---|---|
| 1 | Use the zero adjustment circuit on the control unit to recalibrate output to zero. |
| 2 | Perform a full calibration with standard gas to verify accuracy. |
| 3 | If the problem persists, the sensor assembly is likely damaged. |
| 4 | Replace the detection sensor assembly. |
Important: Sensors exposed to extreme over-range conditions often need replacement. Don’t rely on recalibration alone if you suspect permanent damage.
The Problem:
Over time, dust, oil, and other contaminants accumulate on the rain cover and around the sensor probe. This buildup can:
Physically block gas from reaching the sensor
Create a micro-environment with trapped gases
Chemically interact with the sensing material
The result: The detector may show non-zero readings even in clean air, as contaminants mimic the presence of gas or alter sensor resistance.
✅ Solution:
| Step | Action | Critical Notes |
|---|---|---|
| 1 | Remove the rain cover carefully. | Follow manufacturer instructions. |
| 2 | Clean accumulated dirt thoroughly. | Use a soft brush or compressed air. |
| 3 | DO NOT use solvents | Gasoline, acetone, or other solvents will damage the sensor. |
| 4 | Inspect rain cover for damage. | Replace if cracked, corroded, or missing. |
| 5 | Reassemble and test. | Verify zero reading in clean air. |
Prevention Tip: Establish a regular cleaning schedule based on your environment. Dusty or oily locations may require monthly cleaning.
The Problem:
All gas sensors have a finite lifespan. Over time, the sensitive materials inside gradually lose activity. This natural aging process can cause:
Reduced sensitivity to target gases
Drift in baseline readings
Inability to return to zero in clean air
Typical sensor lifespans:
Catalytic bead sensors: 3-5 years
Electrochemical sensors: 2-3 years
Infrared sensors: 5-10 years
✅ Solution:
| Action | When |
|---|---|
| Replace sensor | When sensor reaches end of rated life, or when recalibration no longer restores accuracy. |
| Replace entire detector | For older units where sensors are no longer available. |
Display error refers to a significant difference between the actual gas concentration and the value shown on the detector. This can be either positive (reading high) or negative (reading low).
The Problem:
All electronic components are affected by environmental conditions. Over time, and especially in harsh environments, internal components can drift from their original calibrated state.
Common contributing factors:
Temperature extremes – Accelerate component aging
High humidity – Causes corrosion and leakage currents
Dust and contaminants – Create conductive paths on circuit boards
Electrical interference – From nearby motors, radios, or power lines
✅ Solution:
| Step | Action |
|---|---|
| 1 | Identify and eliminate potential interference sources. |
| 2 | Move large motors, radios, or other equipment away from detector. |
| 3 | Improve shielding on signal cables. |
| 4 | Perform a full reset and recalibration. |
| 5 | If drift continues, consider relocating detector to a more stable environment. |
Installation Best Practices:
| Environmental Factor | Recommended Practice |
|---|---|
| High temperature | Install in shaded areas; use heat shields |
| High humidity | Use weatherproof enclosures; ensure good seals |
| Excessive dust | Install in cleaner locations; use dust filters |
| Electrical noise | Use shielded cable; separate from power lines |
The Problem:
This is a common human error. During calibration or testing, the wrong type of standard gas is used. Different gases produce different sensor responses. Using methane calibration gas for a detector calibrated for propane, for example, will produce inaccurate readings.
✅ Solution:
| Step | Action |
|---|---|
| 1 | Verify the correct gas type for your detector (check manufacturer specifications). |
| 2 | Obtain the proper calibration gas. |
| 3 | Perform calibration adjustment according to manufacturer instructions. |
| 4 | If the displayed value still cannot reach the standard gas concentration after calibration, the sensor may be faulty. |
| 5 | Replace sensor if necessary. |
Critical Safety Note: Always label calibration gas cylinders clearly and train personnel on proper gas selection.
The Problem:
Sensors are delicate components. They can be damaged by:
| Damage Type | Examples |
|---|---|
| Physical impact | Dropping the detector, striking the sensor, vibration damage |
| Chemical corrosion | Exposure to aggressive chemicals, sensor poisons (silicones, sulfides) |
| Overload | Exposure to concentrations far above measurement range |
| Water ingress | Flooding, high-pressure washdown, condensation |
✅ Solution:
| Step | Action |
|---|---|
| 1 | Confirm sensor damage through testing (failure to calibrate, erratic readings). |
| 2 | Replace the sensor with a new, identical model. |
| 3 | Perform full calibration after replacement. |
| 4 | Document the replacement and update maintenance records. |
Warning: Never attempt to repair a damaged sensor. Replacement is the only safe option.
The best way to handle zero drift and display errors is to prevent them. A structured preventive maintenance program catches problems early.
| Frequency | Task |
|---|---|
| Monthly | Visual inspection; check for dirt, damage, or moisture; verify zero in clean air |
| Quarterly | Bump test with calibration gas to verify response |
| Annually | Full calibration by qualified technician |
| Per manufacturer | Sensor replacement at end of rated life |
Keep records of:
Temperature extremes at detector locations
Humidity levels
Any chemical spills or unusual conditions
Calibration results over time
These records help identify patterns and predict when sensors may need replacement.
A combustible gas detector that isn’t accurate is a detector you cannot trust. Zero drift and display errors aren’t just technical annoyances—they’re safety risks that can lead to missed alarms, false evacuations, and compromised protection.
By understanding the causes of these problems and following systematic troubleshooting procedures, you can:
Quickly restore accurate readings
Identify underlying issues before they cause failures
Extend the life of your detection equipment
Maintain a reliable safety system
Remember: When in doubt about sensor accuracy, replace it. The cost of a new sensor is tiny compared to the cost of a gas explosion.
With years of expertise in gas detection technology, HENAN CHICHENG provides high-quality combustible gas detectors, replacement sensors, and professional calibration services. If you’re experiencing persistent accuracy issues, our technical support team can help diagnose the problem and recommend solutions.
Your safety is our commitment—every reading, every detector.
Visit [here] to learn more about our complete range of gas safety solutions.
