# Gas detector

> Fixed and portable detectors for flammable and toxic gas with ATEX/IECEx or NEC area ratings, and what a request needs: gas, range, alarm levels and area class.

URL: https://jjprojectsok.com/products/industrial-safety/gas-detector  
Español: https://jjprojectsok.com/es/products/industrial-safety/gas-detector  
Updated: 2026-10-16

Device that senses flammable or toxic gas and signals an alarm when the concentration passes a set level.

**In short:** Device that senses flammable or toxic gas and signals an alarm when the concentration passes a set level. JJ Projects sources it to the specification the buyer names. Typical reference, certification: ATEX / IECEx or NEC area classification where required.

## Specification references

- Certification: ATEX / IECEx or NEC area classification where required
- Forms: Fixed and portable
- Data to give: Target gas, range, alarm levels and area classification

> Typical references only. The governing specification is the one on your purchase order or datasheet.

## Typical uses

- Monitoring for combustible gas and H2S around process units and storage
- Personal monitors for entry into vessels and confined spaces
- Fixed detection tied to alarms and shutdown logic in a control system
- Maintenance and shutdown work where gas may be present

## What to include in a request

A request with these details can be quoted without a round of questions. Send what you have and we will ask for the rest.

1. Target gas or gases: combustible, H2S, CO, O2, or a named gas
2. Measuring range and units, for example percent LEL, ppm or percent volume
3. Alarm levels needed, low and high, and the output: relay, 4-20 mA or digital
4. Fixed or portable, and for portable, the number of gases in one unit and the battery type
5. Area classification and the protection type required, for example ATEX, IECEx or NEC Class I Division 1 or 2, with the certificate
6. Sensor technology if the project names one, for example catalytic bead, infrared or electrochemical
7. Calibration gas, accessories and spare sensors, plus the documents required

[Request this item](https://jjprojectsok.com/request-a-quote?item=gas-detector)

## Questions

### What does percent LEL mean?

LEL is the lower explosive limit, the lowest gas concentration in air that can burn. Combustible gas detectors usually read in percent of that limit, so 100 percent LEL means the mixture is at the lower limit. Alarms are set well below it.

### Is a gas detector an approved device for a classified area?

Only when it carries a certification suitable for that area and gas group, such as ATEX, IECEx or an NEC-recognized listing. State the area classification so a suitable model is quoted. We source to the rating you name and do not hold the certification.

### Do gas detectors need calibration?

Yes. Sensors drift and are checked or calibrated with test gas at intervals the manufacturer and the site procedure set. Ask for calibration gas and accessories with the detector.

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## Guides

- [How to write an RFQ for industrial materials](https://jjprojectsok.com/knowledge/how-to-write-an-rfq): What an RFQ for industrial materials must specify: item, size, schedule or class, grade, standard, quantity, MTRs, inspection, packing and Incoterm.
- [Material test reports (MTRs) and EN 10204](https://jjprojectsok.com/knowledge/material-test-reports): What a material test report contains, how EN 10204 types 2.1, 2.2, 3.1 and 3.2 differ, what heat numbers mean, and what to check against the purchase order.

[All industrial safety](https://jjprojectsok.com/products/industrial-safety)