CO₂ Sensor
The oracle of your grow room. A Swiss Sensirion SCD41 measuring CO₂ photoacoustically, with Sensirion temperature and humidity, plus ambient light detection.
One device tells you everything that matters — CO₂ levels, temperature, humidity, VPD, light status, and light pollution. Deploy it and know your environment completely.
Encrypted SMS and telephone voice alerts when parameters exceed your thresholds.
Pay by card, Apple Pay or Google Pay. Free shipping. Prices in AUD.
Everything You Need to Know
Most sensors measure one thing. This one measures everything that matters — and calculates the derived values you actually need.
Photoacoustic CO₂ Sensing
We use the Swiss Sensirion SCD41, which measures CO₂ photoacoustically rather than by the conventional optical path. It's a genuinely different measurement principle, and a more elegant one.
A conventional infrared sensor shines light down a chamber and measures how much the CO₂ absorbs. Accuracy depends on the length of that path and on the light source staying consistent as it ages. The SCD41 instead pulses infrared light into a small sealed chamber, where CO₂ molecules absorb it and warm slightly. The gas expands and contracts with each pulse, producing a faint pressure wave, and a microphone measures that sound. The louder the signal, the more CO₂ is present.
Because it measures a pressure wave instead of light lost across a distance, the chamber doesn't need length to be accurate — the whole sensor is about 10 mm square. It also runs an automatic self-calibration algorithm that tracks the lowest readings it sees over time and anchors them to fresh air, which is why long-term drift is measured in single-digit ppm per year rather than the tens.
The Actual Numbers
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Accuracy
±(50 ppm + 2.5% of reading) from 400 to 1,000 ppm, widening to ±(50 ppm + 3%) up to 2,000 ppm. At a typical 1,200 ppm target that's roughly ±86 ppm.
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Long-term drift
±(5 ppm + 0.5% of reading) per year with self-calibration enabled — the number most sensors quote an order of magnitude higher
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Range
Specified 400 to 5,000 ppm, which covers ambient (~420 ppm) through to heavily supplemented. Reports up to 40,000 ppm outside the specified band.
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Repeatability
±10 ppm typical. Response time is 60 seconds (τ63%), so it reports where the room is heading rather than every individual valve pulse.
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Field calibration
Sit it in fresh air for a few minutes and trigger calibration from the app — no reference gases required
Sensor Specifications
±(50 ppm + 2.5% of reading) at 400–1,000 ppm, specified to 5,000 ppm, ±(5 ppm + 0.5%) drift per year
A discrete sensor, not the CO₂ sensor's internal one. ±0.2°C typical accuracy.
±2% RH typical accuracy, full 0-100% range
High-dynamic-range for light status detection and pollution monitoring
Two Temperature Sensors. Only One Reports to You.
The SCD41 has a temperature and humidity sensor built into it, because photoacoustic measurement has to be compensated for both to stay accurate. That sensor has a job, it does it well, and that job is correcting the CO₂ reading — not telling you how warm your room is.
Sensirion are explicit about the difference. Because that sensor sits inside a device generating its own heat, its temperature output needs an offset applied before you can trust it: the factory default is 4°C, and the datasheet's guidance is that the real figure has to be determined for each individual design in thermal equilibrium, anywhere from 0°C to 20°C depending on enclosure, airflow, and operating mode.
So we fit a discrete Sensirion SHT41 as well, sitting away from that heat, and that's the one whose readings reach you. The temperature on your screen isn't a self-heating correction that somebody estimated. It's a measurement.
The device automatically calculates VPD (Vapor Pressure Deficit) from the temperature and humidity readings — the metric that actually matters for plant transpiration. No manual calculations, no lookup charts. Just the number you need.
Light Awareness
The integrated lux meter isn't for measuring PAR, and it can't be. Lux is weighted to the sensitivity of the human eye, which peaks in green and under-reads the red and blue your plants use most — so two fixtures with identical PPFD can give completely different lux readings. What it's for is knowing what's happening in your room when you're not there.
For actual canopy-level photosynthetic measurement, a dedicated PPFD sensor is in development and will report into the same dashboard.
Dark Cycle Protection
Light pollution during dark periods causes stress, hermaphroditism, and yield loss. The lux sensor gives you proof that dark means dark.
System-Wide Dark Mode
Light data is shared across your OMGROW system. When darkness is detected, every device stops illuminating its indicator LEDs, and devices with screens go black. Equipment that glows through a dark cycle is part of the problem, so ours doesn't.
Hardware & Connectivity
The Device
- • Louvred Stevenson screen housing — air flows through freely while the CO₂ sensor stays isolated from heat-generating components
- • WiFi connectivity — connects directly to your network, or to our optional gateway for areas with limited coverage
- • Standard 5V USB power — any phone charger works as a replacement
- • Over-the-air firmware updates — new features pushed automatically when connected
- • Dark room aware — when the sensors report lights-off, indicator LEDs stay off completely, so the equipment can't pollute your dark cycle
Access From Anywhere
- • TLS-encrypted connection to our servers — monitor from any phone, tablet, or computer, anywhere in the world
- • SMS and phone call alerts — set thresholds for CO₂, temperature, humidity, or VPD and get notified immediately if breached
- • Historical graphs included — 48 hours of real-time data and 7 days of aggregated data, free, no subscription
- • Web app works on any browser. Native Android and iOS apps available.
- • No subscriptions. No monthly fees. One purchase, lifetime access.
Printed in PLA. Built to Be Repaired.
The housing is 3D printed in PLA, a bioplastic made from plant starch. It's mostly polylactic acid, with a small fraction of polymer impact modifiers blended in so it prints cleanly and stands up to years in a warm, humid room. Those modifiers are polymers, not the free-floating phthalate plasticisers that make up to 40 percent of flexible PVC, and there are no bisphenols because PLA isn't a polycarbonate.
Every device carries a five-year warranty, and every part in it is user-replaceable. We sell the circuit boards, the printed cases and the individual parts, so if something does fail outside the warranty you fix it cheaply instead of replacing the device. We'd like you to still be running this in ten years.
Why we build from bioplasticReady to know your grow room completely?
All configurations available with 2 week lead time. Shipping worldwide.