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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

Field guide: LEL and UEL Source-Boundary Guide

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Free source-aware cross-sensitivity planning screen for gas detection technicians, safety engineers, and industrial hygienists. Enter a supported sensor type (catalytic bead, infrared, or PID), calibration gas, target gas, and display reading to see the local response-factor screen. The rows are planning assumptions and source pointers only; they are not a current detector manual, calibration record, compliance method, confined-space permit, exposure assessment, or hot-work approval.

Pro Tip: A methane-calibrated catalytic bead LEL sensor may under-respond to heavier hydrocarbons in many published examples, and a PID response-factor correction is a ppm estimate rather than a %LEL safety result. Always verify the exact sensor model, calibration gas, target gas, environmental conditions, bump test, and site procedure before acting on a reading.

Look up LEL/UEL values for the target gas

LEL/UEL Lookup →

Select the right multi-gas detector for your application

Multi-Gas Detector Guide →

Review H2S source-boundary exposure screens

H2S Exposure Reference →

Look up chemical exposure limits for interfering gases

Chemical Exposure Limits Lookup →

How It Works

  1. Select Sensor Type

    Choose one of the supported local rows: catalytic bead combustible gas/LEL, infrared hydrocarbon response, or PID VOC response-factor screening. Electrochemical toxic-gas rows require the exact sensor manual and are not calculated in this app.

  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 Source-Gap Table

    The tool shows local response-factor rows and flags no-response cases. Correction-factor conventions vary, so the current instrument manual controls the actual factor and formula.

  4. Apply As Planning Math Only

    For supported combustible rows, the app multiplies displayed %LEL by the local correction factor for a single-gas planning screen. PID rows stay in ppm response-factor units and are not %LEL safety results.

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

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

Frequently Asked Questions

Some electrochemical CO sensors have hydrogen or other cross-interference, but this app does not calculate electrochemical toxic-gas rows. Check the manufacturer's cross-sensitivity data for your specific sensor model and treat the alarm under your site procedure.
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 and response-factor rows are preliminary local planning assumptions. They vary by instrument, sensor, lamp, calibration gas, sensor age, temperature, humidity, oxygen level, sample path, concentration range, and gas mixture. This tool is not a substitute for current manufacturer documentation, proper calibration, bump testing, confined-space or hot-work procedures, compliance monitoring, or professional atmospheric assessment.

Guides for this job

Safety

LEL and UEL Source-Boundary Guide

What lower and upper explosive limits mean, how gas detectors use %LEL readings, and why current source data, detector calibration, and site procedures still control.

Read Guide →
Safety

Gas Detector Cross-Sensitivity Explained

How response factors and interfering gases affect detector readings, with source-boundary, calibration, and manufacturer-manual warnings.

Read Guide →
Safety

H2S Detection and Safety Guide

Hydrogen sulfide source-boundary guide covering OSHA, NIOSH, and ACGIH exposure rows, odor limits, detector-review boundaries, and emergency-response caveats.

Read Guide →
Safety

Gas Mixture Flammability Guide

Why 17% oxygen and 15% methane is still a serious problem, how LEL and UEL really behave in mixed atmospheres, and what OSHA requires before entry or hot work.

Read Guide →

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