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Gas Detector Cross-Sensitivity Calculator

Understand how your gas detector responds to gases other than the calibration gas using published cross-sensitivity factors

Free cross-sensitivity reference tool for gas detection technicians, safety engineers, and industrial hygienists. Enter your detector's sensor type (catalytic bead, electrochemical, infrared, PID) and calibration gas to see how the sensor responds to other gases present in the environment. Cross-sensitivity factors from major manufacturers (RAE Systems, MSA, Draeger, Industrial Scientific, RKI) show whether your detector over-reads, under-reads, or does not respond at all to interfering gases. Includes correction factor math so you can convert displayed readings to actual concentrations.

Pro Tip: A catalytic bead LEL sensor calibrated on methane will typically read about 50-60% of actual concentration when exposed to pentane or hexane. This means in a pentane atmosphere at 50% LEL, your methane-calibrated detector might only read 25-30% LEL. The atmosphere is more dangerous than the instrument indicates. Always know what gas you are actually detecting and apply the appropriate correction factor.

Look up LEL/UEL values for the target gas

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Gas Cross-Sensitivity Calculator
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How It Works

  1. Select Sensor Type

    Choose the sensor technology in your detector: catalytic bead (combustible gas/LEL), electrochemical (toxic gases like CO, H2S, SO2, NO2), infrared (CO2, hydrocarbons), or PID (VOCs). Each technology has different cross-sensitivity characteristics.

  2. Select Calibration Gas

    Enter the gas your detector was calibrated with. This is the gas that produces an accurate 1:1 reading. Catalytic bead sensors are typically calibrated on methane or pentane. CO sensors are calibrated on carbon monoxide.

  3. Review Cross-Sensitivity Table

    The tool shows the response factor for each interfering gas. A factor of 0.5 means the detector reads half the actual concentration. A factor of 2.0 means it reads double. A factor of 0.0 means no response at all.

  4. Apply Correction Factor

    Multiply the displayed reading by the correction factor to get the estimated actual concentration. For example, if your methane-calibrated catalytic bead sensor reads 30% LEL in a hexane atmosphere and the correction factor is 1.7, the actual concentration is approximately 30 x 1.7 = 51% LEL. The atmosphere is more dangerous than the display indicates.

Built For

  • Gas detection technicians interpreting readings in multi-contaminant environments
  • Safety engineers evaluating whether existing detector configurations cover all anticipated hazards at a facility
  • Industrial hygienists assessing exposure when the target gas differs from the calibration gas
  • Instrument technicians selecting calibration gas to minimize cross-sensitivity errors for known hazards
  • Emergency responders interpreting portable detector readings at incident scenes with unknown atmospheres

References

  • RAE Systems Technical Note TN-106: Sensor Specifications and Cross-Sensitivities
  • MSA Gas Detection Handbook, Chapter 3: Sensor Technologies and Cross-Sensitivities
  • Draeger Safety: Cross-Sensitivity Data for Electrochemical Sensors
  • ISA-TR12.13.03: Guide for Combustible Gas Detection as a Method of Protection

Frequently Asked Questions

Electrochemical CO sensors have known cross-sensitivity to hydrogen (H2), hydrogen sulfide (H2S), and some organic vapors. If your CO sensor alarms in an environment where CO is unlikely but H2 or H2S is present, the sensor is probably responding to the interfering gas. Check the manufacturer's cross-sensitivity data for your specific sensor model.
Cross-sensitivity factors are approximate and vary between sensor batches, sensor age, and environmental conditions. They are useful for hazard assessment and qualitative interpretation but should not be used for quantitative compliance monitoring. For regulatory compliance, use a detector calibrated on the specific gas being measured, or use analytical methods (detector tubes, laboratory analysis) for the target compound.
Infrared sensors are generally more selective than catalytic bead or electrochemical sensors because they detect specific wavelength absorption bands. However, many hydrocarbons absorb at similar wavelengths, so an IR LEL sensor calibrated on methane will also respond to propane, butane, and other hydrocarbons, though with different response factors. IR CO2 sensors can be affected by water vapor in some designs.
Cross-sensitivity depends on the specific sensor chemistry, electrode formulation, and filter design, which vary between manufacturers and even between sensor generations from the same manufacturer. Always use the cross-sensitivity data published for your specific instrument model and sensor type. Generic cross-sensitivity tables from a different manufacturer may not be accurate for your detector.
Disclaimer: Cross-sensitivity factors are approximate values that vary by sensor model, age, temperature, humidity, and gas concentration. Always consult the manufacturer's technical documentation for your specific instrument. This tool is a reference aid and is not a substitute for proper calibration, bump testing, and professional atmospheric assessment.

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