Carbon dioxide is colourless, odourless and heavier than air. It collects in cellars, pits and low rooms, where it displaces the air and is toxic in its own right at high concentration.
The places this cell is usually ordered for. The detector body and the wiring are the same in every one of them.
The ppm ranges are for air quality and ventilation control. The 0 to 20 %VOL range is for leak detection around bulk CO2 storage, where the concentration can rise far beyond the ppm scale.
The standard unit is 0-5000 ppm at 1 ppm resolution. The other ranges are supplied on request.
Pick the lowest range that still covers the highest concentration you expect at that point. A lower range gives finer resolution around the alarm set points.
Carbon dioxide is heavier than air (relative density 1.53, air = 1), so it settles toward the floor and into pits, ducts and cellars. Mount the detector low, 0.3 to 0.6 m above floor level, close to the likely release point.
Keep the detector clear of splashing water, oil and mechanical impact, and leave room around it to open the cover for calibration.
One detector body across the whole family. The sensing cell inside sets the target gas and the range.
| Target gas | Carbon dioxide (CO2) |
|---|---|
| Selectable ranges | 0-1000 / 2000 / 5000 ppm / 0-20 %VOL |
| Resolution | 1 ppm / 0.01 %VOL |
| Response time (T90) | ≤15 s |
| Sensor | Replaceable carbon dioxide sensing cell |
| Accuracy | ≤±3% FS |
| Repeatability | ≤±1% |
| Sampling | Diffusion, pump suction optional |
| Analogue output | 4-20 mA, 3-wire (2-wire optional) |
| Digital output | RS485, Modbus RTU |
| Alarm outputs | Two relays, normally open, AC 120 V 0.5 A / DC 24 V 1 A |
| Supply | 24 VDC (12 to 30 VDC), 2 W or less |
| Display | LCD with backlight |
| Enclosure | Flameproof aluminium alloy, IP65 |
| Cable entry | M20×1.5 internal thread |
| Mounting | Wall mount or pipe flow-through |
| Operating conditions | -20 to 50 °C, 10 to 95% RH non-condensing |
| Dimensions and weight | 196 × 140 × 91 mm, 1.2 kg |
These are United States values. Limits differ by country, and alarm set points are decided by the site against its own regulations and risk assessment.
| NIOSH recommended exposure limit (REL) | TWA 5000 ppm (9000 mg/m³) ST 30,000 ppm (54,000 mg/m³) |
|---|---|
| OSHA permissible exposure limit (PEL) | TWA 5000 ppm (9000 mg/m³) |
| Immediately dangerous to life or health (IDLH) | 40,000 ppm |
TWA is a time-weighted average over a working shift, ST a short-term limit, C a ceiling that should not be exceeded, and Ca marks a substance NIOSH treats as a potential occupational carcinogen.
Source: NIOSH Pocket Guide to Chemical Hazards: Carbon dioxide
Gas detection has a requirement most sensors do not: the alarm must work when the network does not. The cloud is layered on top of the local interlock, and never replaces it.
Two configurable alarm relays per detector, normally open dry contacts. Fans, solenoid valves and sirens trip locally with no network involved.
The analogue loop feeds a PLC, a DCS or an existing alarm panel directly, so the detector drops into an installed base without replacing it.
The digital reading goes over Modbus RTU into our industrial IoT controllers, on the same bus as the other sensors on the site, and from there to the cloud over cellular.
Concentration charts, threshold alerts to the right person, an exportable log of every excursion, and a REST API for your own reporting system.
The RS485 output is half duplex Modbus RTU. Several detectors share one twisted pair, each with its own address.
| Protocol | Modbus RTU |
|---|---|
| Serial settings | 9600 bps, 8 data bits, no parity, 1 stop bit |
| Default address | 0x01, set from the front panel menu |
| Read function | 0x03, read holding registers |
| Address | Content | Type | Scaling |
|---|---|---|---|
| 0x0000 | Gas concentration | UINT16 | Value ÷ 10^decimals |
| 0x0011 | Decimal places | UINT16 | Direct, 0 to 3 |
| 0x0013 | Full-scale range | UINT16 | Value ÷ 10^decimals |
Request: 01 03 00 00 00 01 84 0A
Response: 01 03 02 03 52 39 49On the standard unit the decimal places register reads 0, so a raw value of 850 is 850 ppm. Read register 0x0011 once on any unit to confirm its scaling.
Heavier. Its relative density is 1.53 against 1 for air, so it settles low. The detector is mounted 0.3 to 0.6 m above floor level, near the likely release point.
0-1000 / 2000 / 5000 ppm / 0-20 %VOL, with a resolution of 1 ppm / 0.01 %VOL. The sensing cell sets the range, so it is chosen when the detector is ordered.
Both words get used for it. The sensor is the sensing cell inside, which reacts to the gas. The detector is the complete instrument around it: the housing, the display, the alarm relays and the outputs. What is described here is the complete detector, with the carbon dioxide sensor cell fitted.
No. The two relays are driven locally by the detector against its configured set points. Ventilation, shut-off and sirens trip even when connectivity is down. The cloud adds the record, remote visibility and escalation on top.
The detector outputs 4-20 mA, RS485 Modbus RTU and two alarm relays at the same time. The Modbus output connects to a Genesis controller alongside the other sensors on the site, and the controller sends the readings over cellular for charts, alerts and the REST API. The analogue loop and the relays keep serving the existing panel and the local interlock.
At least once every six months. Calibration is done from the front panel menu by trained personnel with certified gas: a zero, then a span near half of full scale. The sensing cell is replaced at end of life without changing the installation.
The detectors are built in flameproof aluminium enclosures designed for hazardous area installation, sealed to IP65. Certification documentation for your market and installation class is scoped per order.
How many carbon dioxide points, at what range, and which panel or controller they report into. We come back with the cell and range to specify and how the detectors wire into what is already there.
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