CH4 Detector vs Combustible Gas LEL Detector Malaysia

A customer asking for a “methane detector” may require one of several very different instruments.

They may need to:

• Detect a small methane leak

• Measure methane concentration in ppm

• Monitor methane as a percentage by volume

• Check combustible-gas explosion risk in %LEL

• Protect workers entering a confined space

• Monitor methane continuously using a fixed detector

• Locate methane remotely using optical technology

A CH₄ detector and a combustible gas LEL detector may both respond to methane, but they do not necessarily have the same measurement purpose, range or sensor technology.

Before selecting an instrument in Malaysia, confirm what the customer actually needs to measure.

Quick Comparison

The exact capability depends on the instrument, installed sensor, calibration and approved application.

What Is a CH₄ Detector?

A CH₄ detector is intended to detect or measure methane.

Depending on the application, methane may be displayed as:

• ppm

• % volume

• %LEL

A methane-specific detector may use:

• Catalytic combustion

• Infrared absorption

• Semiconductor sensing

• Laser-based optical detection

• Another approved methane-sensing principle

The correct technology depends on the required range, environment, response, selectivity and installation method.

The words “CH₄ detector” alone are not enough to select a model.

What Is an LEL Detector?

LEL means Lower Explosive Limit.

The LEL is the minimum concentration of a combustible gas in air that can support ignition under specified conditions.

A reading shown as %LEL indicates how close the measured atmosphere is to the configured lower explosive limit.

For example, a display of 10%LEL does not mean that the atmosphere contains 10% gas by volume.

It means the reading corresponds to 10% of the configured LEL scale.

The actual conversion depends on:

• Gas

• LEL value used by the instrument

• Calibration gas

• Target gas

• Sensor response

• Instrument configuration

Always follow the manufacturer’s documentation instead of applying an assumed conversion.

ppm vs %Vol vs %LEL

These units answer different questions.

ppm

ppm means parts per million.

It is often used for relatively low gas concentrations.

For methane:

• 10,000 ppm equals 1% by volume mathematically.

• However, a detector must still be designed and configured for the required range.

• A low-range ppm methane detector is not automatically suitable for measuring high concentrations.

%Vol

%Vol indicates the percentage of gas by volume in the atmosphere or sample.

It may be used when the expected methane concentration is much higher than a low ppm range.

%LEL

%LEL expresses the result relative to the gas’s lower explosive limit.

It is commonly used for combustible-gas safety screening.

Do not treat ppm, %Vol and %LEL as interchangeable labels.

The required unit should be confirmed before purchasing the detector.

Is 100%LEL the Same as 100% Methane?

No.

100%LEL does not mean 100% methane by volume.

It indicates that the measured concentration has reached the configured lower explosive limit for the target or reference gas.

A gas concentration can reach 100%LEL while still representing only a small percentage of the total atmosphere by volume.

This is why a customer must specify whether the requirement is:

• Low-level methane detection

• Combustible-risk monitoring

• High-concentration methane measurement

• Process-gas measurement

The same instrument may not cover all four applications.

Can an LEL Detector Detect Methane?

Many LEL detectors can detect methane when equipped with a suitable sensor and calibration.

However, confirm:

• Sensor type

• Calibration gas

• Measurement range

• Display unit

• Cross-sensitivity

• Required oxygen condition

• Operating temperature

• Pressure limitation

• Applicable certification

An instrument calibrated for methane may respond differently to propane, butane, hydrogen or other combustible gases.

A displayed %LEL result should be interpreted according to the manufacturer’s gas-response information.

Can a Methane Detector Detect Every Combustible Gas?

No.

A methane-specific sensor may not respond correctly—or at all—to every combustible gas.

For example, different sensing technologies have different limitations:

• A methane-selective laser detector may be intentionally insensitive to many other gases.

• An infrared hydrocarbon detector may not be suitable for gases without the required infrared absorption characteristics.

• A catalytic sensor may respond to several combustible gases, but the sensitivity can differ from one gas to another.

• A detector calibrated for methane may under-read or over-read another gas.

Never assume that “combustible” means “equally detectable by any LEL sensor.”

Catalytic LEL Sensor

A catalytic-bead sensor detects combustible gas through oxidation on a heated sensor element.

It may be suitable for detecting a range of combustible gases, depending on the sensor and calibration.

Important considerations include:

• Sufficient oxygen

• Sensor poisoning

• Inhibiting gases

• Calibration gas

• Target-gas response

• Temperature

• Sensor ageing

Certain chemicals may reduce the sensitivity of a catalytic sensor.

A detector that powers on normally may still fail to respond correctly if the sensor has been poisoned or damaged.

This is one reason regular bump testing is important.

Infrared LEL or Methane Sensor

An infrared sensor measures gas by infrared absorption.

Potential advantages may include:

• No catalytic combustion

• Suitability for selected hydrocarbons

• Resistance to some catalytic sensor poisons

• Stable operation in appropriate applications

However, an infrared sensor does not automatically detect every combustible gas.

The user must confirm:

• Target gas

• Optical response

• Measurement range

• Environmental limitations

• Calibration method

• Sensor approval

An infrared hydrocarbon sensor should not be assumed to detect hydrogen unless the manufacturer specifically states that capability.

TDLAS Methane Detector

A TDLAS detector uses a selected laser wavelength to detect methane absorption.

This method may be suitable for:

• Methane-specific leak detection

• Open-path monitoring

• Remote inspection

• Selected fixed systems

• Specialised industrial applications

Because the optical wavelength is selected for methane, the system may provide better methane selectivity than a general combustible-gas detector.

However, performance can still be affected by:

• Optical-path condition

• Temperature

• Pressure

• Distance

• Alignment

• Dust or obstruction

• Instrument configuration

A laser methane detector serves a different purpose from a personal four-gas confined-space detector.

Which Detector Is Suitable for Confined Spaces?

Confined-space assessment often requires more than combustible-gas measurement.

The required measurements may include:

• Oxygen

• Combustible gas

• Hydrogen sulphide

• Carbon monoxide

• Other site-specific toxic gases

A methane-only detector cannot confirm that oxygen is safe.

It also cannot detect every toxic gas hazard.

The detector configuration must follow the site risk assessment, entry procedure and gases reasonably expected to be present.

Gas-testing order, sampling locations, ventilation and continuous monitoring should follow the approved confined-space procedure.

Diffusion vs Pump Sampling

Diffusion Detector

Gas reaches the sensors naturally through the atmosphere.

It may be suitable for:

• Personal monitoring

• Area monitoring

• Continuous use near the worker

• General leak warning

Pump-Type Detector

An internal or external pump draws a sample through tubing.

It may be suitable for:

• Pre-entry checks

• Tanks

• Manholes

• Remote sampling

• Difficult-to-reach areas

• Checking different depths

For pump sampling, consider:

• Tubing length

• Sample travel time

• Filter condition

• Water trap

• Pump flow

• Leakage

• Condensation

• Gas absorption by the tubing

Allow enough time for the sample to reach the sensor before accepting the reading.

Portable vs Fixed LEL Detection

Portable Detector

Portable instruments may be used for:

• Personal protection

• Pre-entry atmosphere checks

• Maintenance

• Temporary monitoring

• Leak investigation

• Contractor work

Fixed Detector

Fixed systems may be used for:

• Continuous plant monitoring

• Gas-storage rooms

• Process areas

• Machinery rooms

• Automatic ventilation control

• Sirens and warning lights

• Remote alarms

• Control-system outputs

Fixed-detector selection also requires a proper sensor-location study.

Consider:

• Gas density

• Leak source

• Air movement

• Ventilation

• Obstructions

• Maintenance access

• Weather exposure

• Alarm response

Do not install a fixed detector based only on an assumed “high” or “low” location without assessing the actual release and airflow.

Why Calibration Gas Matters

A combustible-gas detector may be calibrated using methane but used in an area where another combustible gas is expected.

The response to the target gas may be different.

Before use, confirm whether the manufacturer requires:

• Methane calibration

• Propane calibration

• Target-gas calibration

• A correction factor

• A special sensor

• Different alarm settings

Do not copy correction factors between different brands or sensor models.

The instrument can only be as reliable as its approved calibration and testing process. OSHA guidance recommends using suitable traceable test gas and following the manufacturer’s instructions for portable gas monitors.

Bump Test vs Full Calibration

Bump Test

A bump test confirms that:

• Gas reaches the sensor

• The sensor responds

• The display changes

• Audible alarm works

• Visual alarm works

• Vibration alarm works

• Pump and sample path operate where applicable

Full Calibration

A full calibration checks and adjusts the instrument response using a known gas concentration.

A passed bump test does not replace calibration when calibration is required.

A detector that fails a bump test should be removed from safety use until it has been checked according to the approved procedure.

Why Oxygen Level Matters

Some catalytic combustible-gas sensors depend on oxygen for the sensing reaction.

If the atmosphere contains insufficient oxygen, the LEL reading may not behave as expected.

This creates an important risk:

A low combustible-gas reading in an oxygen-deficient atmosphere does not automatically mean the atmosphere is safe.

For confined-space and unknown-atmosphere work, oxygen, combustible and relevant toxic gases must be assessed according to the approved procedure.

Common Selection Mistakes

Asking Only for a “Methane Meter”

The supplier still needs the range, unit, application and sensor requirement.

Confusing ppm with %LEL

A low-level leak detector and an explosion-risk meter may require different instruments.

Assuming Every Four-Gas Detector Measures Methane in ppm

Many four-gas detectors display the combustible channel in %LEL.

Assuming Every LEL Detector Detects Hydrogen

Sensor technology must be confirmed.

Ignoring the Calibration Gas

Response to the actual target gas may differ.

Using a Methane-Only Detector for Confined-Space Clearance

Other hazards may remain undetected.

Skipping the Bump Test

A normal display does not prove that the sensor and alarm respond to gas.

Selecting a Fixed Detector Without Planning the Location

Poor placement may delay or prevent gas from reaching the sensor.

Which Detector Should You Choose?

Choose a CH₄-specific detector when:

• Methane selectivity is important

• The required result is methane in ppm or %Vol

• The application is methane leak detection

• Remote optical methane detection is required

• Other combustible gases should not dominate the reading

Choose a combustible gas LEL detector when:

• The objective is explosion-risk screening

• The reading must be displayed in %LEL

• Several combustible gases may be present

• The detector is part of a multi-gas safety instrument

• Site procedures specify LEL monitoring

Choose a fixed methane or LEL system when:

• Continuous monitoring is required

• Automatic alarms or outputs are needed

• The area is normally unattended

• Ventilation control is required

• Gas release could occur at any time

The final choice must follow the known gas hazards and site risk assessment.

Information to Send Before Requesting a Quotation

Provide:

• Target gas

• Other gases present

• Required range

• ppm, %Vol or %LEL

• Portable or fixed use

• Diffusion or pump sampling

• Indoor or outdoor environment

• Temperature and humidity

• Atmospheric or process pressure

• Alarm requirements

• Output requirements

• Hazardous-area classification

• Required certification

• Quantity

Without these details, two instruments described as “methane detectors” may provide completely different functions.

Need Help Selecting a CH₄ or LEL Detector in Malaysia?

Send MTM Precision your gas name, required unit, expected range, site condition and application.

We can help identify whether the requirement is for:

• Methane ppm detection

• Methane %Vol measurement

• Combustible-gas %LEL monitoring

• Portable multi-gas detection

• Pump-sampling inspection

• Fixed gas monitoring

• Methane-specific optical detection

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