SEMEATECH · COMBUSTIBLE GAS SENSORS

SemeaTech 4LEL-3.0 Combustible Gas Sensor

SemeaTech 4LEL family sensor; manufacturer product photo — Manufacturer family illustration; the exact 4LEL-3.0 configuration may differ.

Catalytic-combustion sensing component for combustible-gas concentration measurement; engineering integration and calibration depend on the target gas.

Manufacturer: SemeaTech

Technical Specifications

Measurement	Combustible gases, %LEL
Sensing principle	Catalytic combustion
Nominal range	0–100% LEL
Typical T90	<30 s
Resolution	<1% LEL
Recommended supply	3.00 ± 0.02 VDC
Operating temperature	−30 to 50°C

Official Technical Source

Manufacturer model page and specifications →

Specifications refer to the listed model and may vary by revision, configuration, sensor installation and calibration. Confirm the current official datasheet. A sensor element is not a certified gas detector or safety instrument by itself.

4LEL-3.0 — catalytic combustible bridge and poisoning sensitivity — original maker engineering data

Measured range, current output and lifecycle apply to the specified SemeaTech model rather than the whole sensor family.

Attribute	Original manufacturer data	Application significance
Sensing principle	Catalytic combustion-type 4-Series LEL bridge element	Not an optical infrared hydrocarbon module; requires oxygen for catalytic reaction.
Span / overload	0–100% lower explosive limit, maximum overload 100% LEL per maker	A %LEL scale depends on calibration gas and combustible mixture.
Bridge / power	3.00 ±0.02 V DC, 95 ±15 mA	Voltage and matching bridge electronics affect calibration; not a loop-powered sensor.
Sensitivity	22 ±7 mV per %CH₄ according to OEM	The sensor output is millivolt bridge signal, not 4–20 mA.
T90 / resolution	T90 <30 s, resolution below 1% LEL	Dynamic response depends on diffuser and gas exposure.
Operating conditions	−30 to +50 °C, 0–90% RH noncondensing	Heavy contamination or condensate can inhibit diffusion.
Poisons	Maker documents ~20% sensitivity change after H₂S challenge and ~40% after HMDS test	Siloxanes/sulfides can poison pellistors; gas bump test essential.

Integration, cross-sensitivity and maintenance

A catalytic flammable sensor cannot be specified for oxygen-depleted inerted tanks as though it were an infrared detector. Bridge voltage must be matched to 3.0V specification, and sensor response depends on methane/hydrocarbon reference gas and LEL conversion. Exposure to siloxane or sulfur compounds can reduce catalytic response, leading to unsafe low readings: schedule qualified bump/calibration tests and replace contaminated elements. A raw sensing bridge does not establish a complete control panel’s explosion-protection rating.

Primary SemeaTech source: Original product model information and technical sheets. Confirm current exact part code, supply revision and regional certification before an approved installation.

AirAlign independent editorial analysis · 25 October 2026. OEM sensor data do not grant completed gas instrument certification.