Gas Detector Alarm Level Calculator

Work out gas detector alarm level instantly with clear inputs, formula shown and shareable results.

About Gas Detector Alarm Level Calculator

One percent by volume is 10,000 ppm, so a gas with a five percent lower explosive limit reaches it at 50,000 ppm. Flammability alarms are conventionally set at ten percent of LEL, but for most solvents the occupational exposure limit is a tiny fraction of the LEL, so a flammability alarm gives no toxicological protection at all.

Formulas

Unit conversion

LEL in ppm = LEL percent by volume x 10,000

Alarm level

Alarm ppm = LEL ppm x alarm percentage of LEL

Worked example

With the default values below, Gas Detector Alarm Level Calculator returns Alarm level in ppm of 5,000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lower explosive limit of the gasaccepts 0.1–30 % by volume: 5 % by volume
Alarm set pointaccepts 1–50 % LEL: 10 % LEL
Occupational exposure limitminimum 0.1 ppm: 100 ppm

Results

Alarm level in ppm: 5,000 ppm
Lower explosive limit in ppm: 50,000 ppm
Alarm level by volume: 0.5000 % by volume
Exposure limit expressed as percent LEL: 0.2000% % LEL

Step by step

1Values used
2Unit conversion
3Alarm level
4Alarm level in ppm= 5,000 ppm
5Lower explosive limit in ppm= 50,000 ppm
6Alarm level by volume= 0.5000 % by volume
7Exposure limit expressed as percent LEL= 0.2000 % LEL

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Gas detection design, alarm set points and calibration must follow the applicable standard and the detector manufacturer's instructions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Gas detection design, alarm set points and calibration must follow the applicable standard and the detector manufacturer's instructions.

Frequently Asked Questions

How is the Gas Detector Alarm Level figure worked out?

LEL in ppm = LEL percent by volume x 10,000. One percent by volume is 10,000 ppm, so a gas with a five percent lower explosive limit reaches it at 50,000 ppm.

Can one detector cover both risks?

Only if it has both a flammability and a toxicity sensor. A catalytic bead LEL sensor cannot resolve the low concentrations that exposure limits demand.

What values do I need to enter?

This calculator takes 3 inputs: Lower explosive limit of the gas, Alarm set point, Occupational exposure limit. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.