Why Temperature Can Affect Methane Detector Readings Malaysia

A methane detector may perform correctly during calibration but show a different response when used in a hot plant room, cold storage area, outdoor tank farm or high-pressure process environment.

This does not automatically mean that the instrument is defective.

Gas-detector performance can be influenced by:

• Sensor technology

• Ambient temperature

• Atmospheric pressure

• Humidity

• Oxygen concentration

• Calibration gas

• Target gas

• Sampling method

• Sensor condition

• Interfering gases

For safety applications in Malaysia, users should check the instrument’s approved operating conditions and follow the manufacturer’s bump-test and calibration instructions.

Why Does Temperature Matter?

A gas sensor converts a chemical or physical interaction into an electrical signal.

Changes in temperature can affect:

• Chemical reaction rate

• Sensor sensitivity

• Electronic response

• Optical absorption

• Gas density

• Pump performance

• Battery performance

• Zero stability

• Response and recovery time

Different sensor technologies respond differently.

A temperature effect reported for an optical methane detector should not automatically be applied to a catalytic-bead, infrared or semiconductor detector.

What Recent Methane Research Shows

Recent research studied the effect of temperature and pressure on several optical methane-retrieval methods near a specific infrared wavelength.

Under the study’s modelled conditions, temperature changes created a larger calibration-transfer bias than many users might expect. Pressure changes also affected the reported methane result.

However, the research focused on specialised optical methods.

Its numerical results should not be directly applied to:

• OTYWELL portable gas detectors

• Wintact combustible gas detectors

• Benetech gas detectors

• Catalytic-bead LEL sensors

• Electrochemical toxic-gas sensors

• Every infrared methane detector

The practical lesson is broader:

A gas detector’s performance depends on both its sensor technology and the conditions under which it is used.

Methane Detector vs Combustible Gas Detector

These descriptions are often confused.

Methane-Specific Detector

A methane-specific detector is configured or designed to measure methane.

Depending on the model and technology, the result may be displayed as:

• ppm

• % volume

• %LEL

• Another specified unit

Combustible Gas or LEL Detector

A combustible gas detector measures the presence of flammable gas relative to its lower explosive limit.

Many LEL instruments are calibrated using methane or another specified gas.

The response to a different combustible gas may not be identical.

TDLAS Methane Detector

Tunable diode laser absorption spectroscopy uses a selected optical wavelength to detect methane.

It may provide more selective methane measurement for suitable applications, but performance still depends on the optical path, environmental conditions, gas concentration and instrument design.

Do not assume that all three instrument types are interchangeable.

Temperature and Catalytic-Bead Sensors

Catalytic-bead sensors detect combustible gas through controlled oxidation on a heated sensor element.

Their performance may be affected by:

• Ambient temperature

• Oxygen availability

• Sensor poisons

• Inhibitors

• Ageing

• Gas type

• Calibration gas

• Flow around the sensor

Catalytic combustion requires oxygen.

The sensor may not respond normally in an oxygen-deficient or oxygen-enriched environment unless the instrument is specifically designed and approved for that condition.

Silicones, lead compounds, sulphur compounds and other contaminants may reduce sensor sensitivity, depending on the sensor design.

A bump test helps confirm that gas can reach the sensor and that the instrument responds and alarms. OSHA advises users of portable direct-reading gas monitors to follow the manufacturer’s testing instructions and use suitable, traceable calibration gas.

Temperature and Infrared Methane Sensors

Infrared sensors detect gas by measuring the absorption of infrared energy.

Potential advantages may include:

• No reliance on catalytic combustion

• Resistance to certain catalytic poisons

• Suitability for selected hydrocarbon applications

• Longer-term stability in suitable systems

However, infrared detection may still be affected by:

• Temperature

• Pressure

• Humidity

• Optical contamination

• Gas-path length

• Calibration model

• Target-gas absorption characteristics

An infrared combustible-gas sensor may not detect every flammable gas equally.

For example, the user should not assume that one methane-configured infrared sensor is suitable for hydrogen or every refrigerant.

Why Pressure Can Change the Reading

Pressure can influence:

• Number of gas molecules within the sensing path

• Gas density

• Optical absorption behaviour

• Sample delivery

• Pump flow

• Calibration transfer

This matters when measurements are taken in:

• Pressurised systems

• Vacuum systems

• High-altitude locations

• Enclosed sampling lines

• Process chambers

• Areas with strong pressure fluctuations

A normal portable atmospheric gas detector should not be connected directly to a pressurised gas source unless the manufacturer has provided an approved sampling arrangement.

Excessive pressure or flow may damage the sensor or create an incorrect response.

Why Humidity Matters in Malaysia

Malaysia’s high humidity can affect some gas-detection applications.

Possible effects include:

• Condensation

• Water entering the sensor opening

• Optical-window contamination

• Changes in electrochemical sensor response

• Blocked filters

• Sampling-tube moisture

• Slower gas transport

• Corrosion of connectors

• Pump or flow problems

A detector moved from an air-conditioned room into a hot and humid outdoor area may experience condensation.

Allow the instrument to stabilise according to the manufacturer’s instructions before relying on the reading.

Do not cover the sensor opening or block airflow in an attempt to protect the detector from humidity.

Use only approved accessories and protective arrangements.

Direct Sunlight and Hot Surfaces

A detector left inside a vehicle or placed on a hot metal surface may become much hotter than the surrounding air.

This may affect:

• Sensor response

• Zero stability

• Display

• Battery

• Pump

• Electronic components

When taking measurements outdoors:

• Keep the instrument within its specified operating range

• Avoid leaving it under direct sunlight unnecessarily

• Do not place it on a hot pipe or tank

• Allow it to stabilise after a large temperature change

• Check for condensation

• Perform the required functional checks

The instrument should measure the atmosphere—not the temperature of the surface on which it was placed.

Calibration Temperature vs Site Temperature

A detector calibrated in an air-conditioned room may later be used in a much hotter work area.

Where practical, the calibration and field conditions should be reasonably representative of the intended atmosphere, subject to the manufacturer’s instructions.

OSHA technical guidance states that direct-reading instruments should be calibrated immediately before testing at or near the temperature of the atmosphere being tested when this is applicable to the instrument and task.

This does not mean users should perform unauthorised adjustments in a hazardous area.

Calibration must be conducted:

• In a safe location

• By trained personnel

• Using the correct adapter and flow

• With suitable certified gas

• According to the manufacturer’s procedure

What Is a Bump Test?

A bump test briefly exposes the detector to a known test gas to confirm that:

• Gas reaches the sensor

• The sensor responds

• The display changes

• Audible alarm operates

• Visual alarm operates

• Vibration alarm operates

• Pump and sample path work, where applicable

A bump test is a functional test.

It does not provide the same quantitative adjustment or assessment as a full calibration.

If the instrument fails the bump test, remove it from safety use and follow the approved inspection, calibration or repair procedure.

What Is Calibration?

Calibration compares and adjusts the detector response using a known gas concentration under specified conditions.

Important factors include:

• Correct calibration gas

• Certified concentration

• Gas-cylinder expiry date

• Correct regulator

• Correct flow rate

• Correct adapter

• Stable instrument condition

• Completed warm-up

• Correct sensor channel

• Safe ventilation

Using the wrong gas, flow or concentration can create misleading results.

Calibration should follow the specific instrument manual, site procedure and applicable regulatory requirements.

Why Target Gas and Calibration Gas Matter

A combustible-gas detector may be calibrated using methane but used to detect another hydrocarbon.

The response to the target gas may differ.

Depending on the instrument, the manufacturer may provide:

• Correction factors

• Target-gas calibration

• Cross-calibration guidance

• Sensor-specific response tables

• Restrictions on suitable gases

Do not apply a correction factor from one detector model to another.

If the target gas is known, tell the supplier:

• Gas name

• Expected concentration

• Required unit

• Temperature

• Pressure

• Humidity

• Sampling method

• Application area

This information is necessary before selecting the detector.

What If the Methane Reading Changes with Temperature?

Use a controlled checking process.

Step 1 – Confirm the Instrument Range

Check whether the detector is operating within its specified temperature and humidity range.

Step 2 – Allow It to Stabilise

After moving between very different environments, allow the detector to stabilise according to its manual.

Step 3 – Check for Condensation

Inspect the sensor inlet, filter and sampling path.

Step 4 – Confirm the Gas and Unit

Make sure the detector is configured for the intended gas and measurement unit.

Step 5 – Conduct the Required Bump Test

Use the correct test gas and approved procedure.

Step 6 – Review Calibration Status

Check the calibration date and whether the instrument can hold calibration.

Step 7 – Check the Pump and Sample Line

For pump-type instruments, inspect:

• Tubing

• Filter

• Probe

• Flow alarm

• Blockage

• Leakage

• Condensation

Step 8 – Compare Under Controlled Conditions

If the reading remains questionable, compare the detector using suitable test gas under controlled conditions.

Do not test the detector using an uncontrolled release of flammable gas.

Common Methane Detector Selection Mistakes

Selecting by Gas Name Alone

The same gas may require different instruments depending on the range, unit and application.

Confusing ppm with %LEL

These units answer different monitoring questions and should not be treated as interchangeable.

Ignoring Temperature and Humidity

A model suitable for an indoor plant room may not be suitable for outdoor or high-temperature work.

Assuming Every LEL Sensor Responds Equally to Every Gas

Sensor response depends on the technology, calibration gas and target gas.

Ignoring Oxygen Requirements

Catalytic sensors may depend on sufficient oxygen for normal operation.

Skipping Bump Testing

A powered-on display does not prove that gas can reach the sensor or trigger the alarm.

Using an Expired Calibration Cylinder

The actual gas concentration may no longer be reliable.

Connecting Directly to Process Pressure

Portable detectors may require a pressure-reducing or approved sampling arrangement.

Information Required Before Selecting a Methane Detector

Provide:

• Target gas

• Other gases present

• ppm, %volume or %LEL requirement

• Expected concentration

• Ambient temperature

• Pressure

• Relative humidity

• Indoor or outdoor use

• Diffusion or pump sampling

• Portable or fixed installation

• Alarm requirements

• Output requirement

• Hazardous-area classification

• Required certification

• Number of units

These details help determine whether the application requires a catalytic LEL detector, infrared sensor, methane-specific detector, pump-sampling instrument or fixed monitoring system.

Portable vs Fixed Methane Detection

Portable Detector

Suitable applications may include:

• Personal protection

• Pre-entry checks

• Leak investigation

• Maintenance work

• Temporary monitoring

• Confined-space assessment as part of an approved procedure

Fixed Detector

Suitable applications may include:

• Continuous plant monitoring

• Machinery rooms

• Gas-storage areas

• Process installations

• Automatic alarm systems

• Ventilation control

• Remote monitoring

Fixed detector selection also requires consideration of sensor location, gas behaviour, airflow, power supply, output signal, alarm devices and maintenance access.

Need Help Selecting a Methane or Combustible Gas Detector?

Send MTM Precision:

• Gas name

• Measurement range

• Required unit

• Site temperature and pressure

• Humidity and weather exposure

• Portable or fixed requirement

• Diffusion or pump sampling

• Alarm and output requirements

• Hazardous-area classification

• Site photographs or specification

This information helps determine whether the application requires a methane-specific detector, LEL combustible-gas detector, pump-type portable instrument or fixed gas monitoring system.

MTM Precision supplies gas-detection instruments for factories, contractors, utilities and safety teams in Selangor, Kuala Lumpur, Johor, Penang and throughout Malaysia.

Always follow the instrument manual, workplace risk assessment and approved safety procedure. A gas detector should not be the only control used for a hazardous atmosphere.

MTM Precision Sdn Bhd
Showroom & Service Centre: No. 29-1 & 29-2, Jalan Bandar 18, Pusat Bandar Puchong, 47160 Puchong, Selangor, Malaysia
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my