Question 1

Is the Lower Explosive Limit (LEL) the same as the alarm setpoint?

Accepted Answer

No. LEL is the minimum concentration at which a gas can ignite; for methane it is about 5% by volume, which equals 100% LEL on the detector scale. Alarm setpoints are set well below it, typically at or below 25% LEL for the first-level alarm, according to the local code that governs the project.

Question 2

Where should a household combustible gas detector be installed?

Accepted Answer

Mount according to gas density: for natural gas (methane, lighter than air) install high, close to the ceiling; for LPG (heavier than air) install low, close to the floor. Keep the detector within a few metres of the appliance and away from extractor hoods, steam and direct airflow.

Question 3

Why do oxygen detectors use %VOL instead of ppm?

Accepted Answer

Normal air contains about 20.9% oxygen by volume, so oxygen deficiency and enrichment are tracked as volume percentages. Common reference alarm points are 19.5% VOL for deficiency and 23.5% VOL for enrichment, which are far easier to read and configure in %VOL than in hundreds of thousands of ppm.

Question 4

Can a Shield gas detector shut off the gas supply automatically?

Accepted Answer

Yes. Shield household detectors drive a solenoid valve when the alarm setpoint is reached, and the JYFJS-011 emergency shut-off valve can be triggered by gas alarm systems, fire-protection panels or smart terminals. The valve must be reopened manually so gas cannot return before the hazard is cleared.

Question 5

What is the difference between a stand-alone and a bus-type point gas detector?

Accepted Answer

A stand-alone detector such as the SD2130 series alarms locally and drives linkage outputs without a controller, ideal for single zones. Bus or branch-line detectors such as the SD2100A series report to a gas alarm controller (SD8001A/B) installed in a non-hazardous control room for centralized multi-point monitoring.

Question 6

Does Shield offer OEM and ODM gas detectors?

Accepted Answer

Yes. With 80+ marketable product models and in-house R&D, Shield supports private labelling, housing and packaging customization and configuration changes for distributors and brand owners. Request the catalog to review available platforms.

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