Atmosense Core CO₂ NDIR sensing
Measured, not estimated.
Some lower-cost monitors don't measure CO₂ at all. They estimate a figure (eCO₂) from a gas sensor, so the number can move for reasons that have nothing to do with ventilation.
Atmosense Core CO₂ and Atmosense Core Max both use a dedicated NDIR (non-dispersive infrared) sensor designed specifically for CO₂ measurement. Core Max adds a laser particle sensor, plus a semiconductor gas sensor for TVOC and formaldehyde.
What each sensor does, with published specifications.
- Core CO₂ & Core MaxNDIR CO₂Measures carbon dioxide directly, using infrared light.Range: 400–5,000 ppmAccuracy: ±(50 ppm + 5% of reading)Resolution: 1 ppm
- Core MaxLaser particle sensorCounts fine particles in the air, with its own built-in fan.Measures PM1.0, PM2.5, and PM10Range: 0–1,000 μg/m³Accuracy: ±10 μg/m³ (0–100 μg/m³), ±10% (100–500 μg/m³)Resolution: 1 μg/m³
- Core MaxSemiconductor gas sensorReacts to gases such as VOCs and formaldehyde.TVOC range: 0–9.999 mg/m³HCHO range: 0–1.999 mg/m³Readings are indicative
- Core CO₂ & Core MaxTemperatureShows how warm the room is.Range: 0–50 °CAccuracy: ±1 °C
- Core CO₂ & Core MaxRelative humidityShows how damp the room is, which matters for condensation.Range: 0–99 %RHAccuracy: ±5 %RH
- Core CO₂ & Core MaxLight and proximity sensingLooks after the screen, not the air.Adjusts screen brightness to the roomWakes the screen when you wave your hand near it
At a reading of 1,000 ppm, the CO₂ result is within about ±100 ppm. Full specifications: Core CO₂ → · Core Max →
From room air to CO₂ reading, in five stages.
- Air in: air from the room drifts into the sensor's small measuring chamber through the air inlet.
- Infrared light: a tiny light source shines infrared light across the chamber.
- CO₂ absorbs: CO₂ molecules absorb infrared light at one particular wavelength. The more CO₂ in the chamber, the more of that light is absorbed.
- Detector measures: an optical filter lets only that wavelength through to a detector, which measures how much light made it across.
- Reading delivered: the monitor converts this into parts per million (ppm), shows it on the display with a colour indicator, and sends it to the app over Wi-Fi.
How Core Max senses particles and gases.
Laser particle sensing
A small fan draws a steady flow of room air through the sensor, where a laser beam crosses it. Each particle that passes scatters a flash of light onto a detector. The sensor counts these flashes and uses their strength to sort particles by size, then works out how much PM1.0, PM2.5, and PM10 is in the air, in micrograms per cubic metre (μg/m³).
Because it counts particles as they pass, you can watch levels change as you cook, light candles, or use a wood burner.
Semiconductor gas sensing
A heated sensing surface changes its electrical resistance when gases such as VOCs and formaldehyde reach it. The monitor turns that change into TVOC and HCHO readings, in milligrams per cubic metre (mg/m³).
This type of sensor reacts to many gases at once, so the readings are indicative. They're best for showing when levels rise and fall, rather than giving exact concentrations.
Core CO₂ and Core Max, side by side.
Both share the same NDIR CO₂ sensor. Core Max adds particle and gas sensing.
| Sensors and features | Core CO₂ | Core Max |
|---|---|---|
| NDIR CO₂ sensor | ||
| Temperature and humidity | ||
| PM2.5 (laser particle sensor) | ||
| PM1.0 and PM10 | ||
| TVOC (volatile organic compounds) | ||
| Formaldehyde (HCHO) | ||
| Colour-coded readings on the display | ||
| Screen wakes with a wave | ||
| Brightness adjusts to the room | ||
| Phone alerts and history graphs in the app | ||
| Works with Amazon Alexa and Google Home | ||
| Detects carbon monoxide (CO) |
With Alexa and Google Home, you can ask for the room's temperature and humidity. Air quality readings are shown on the monitor and in the app.
Calibration, power, and placement.
Core CO₂ calibrates itself
After 24 hours powered on, Core CO₂ uses the lowest CO₂ level from the past 24 hours as its fresh-air baseline. Make sure the room is ventilated at some point each day so that baseline is genuinely fresh air.
You can also calibrate it manually: place the monitor in fresh air (about 400 ppm, outdoors or by an open window) for 5–10 minutes, then press the button 3 times quickly.
Power and screen
Both monitors run on USB-C power (5 V ⎓ 2 A). For 24/7 monitoring, keep them plugged into a USB mains plug rated 5V/2A (not included). Core CO₂ also has a built-in 1200 mAh battery, giving up to 13 hours of portable use, and a full charge takes about 2–3 hours.
Both screens turn off after 30 seconds to save power and wake when you wave your hand near them. On Core Max, you can change the timing in the app.
Placement: keep your monitor on a flat, dry surface out of direct sunlight, and don't block the air inlet or vents. Keep it away from your face, as your breath raises the CO₂ reading. Perfume, alcohol, cleaning products, cooking fumes, and similar everyday sources can also affect readings.
What the sensors do well, and where their limits are.
The pros
- Measures CO₂ directly with a dedicated NDIR sensor in both monitors, with accuracy published in the specifications.
- Counts particles with a laser: Core Max's particle sensor has its own fan to draw room air through it.
- Readable at a glance: a full-colour display with colour-coded readings, no phone needed.
- Phone alerts and history: set your own alert thresholds and see daily, weekly, and monthly charts in the app.
- No hub needed: both connect straight to your home Wi-Fi.
The limits
- TVOC and formaldehyde readings are indicative: they show when levels change, not exact concentrations.
- Core CO₂ measures CO₂, temperature, and humidity only: for particles and fumes, you'll need Core Max.
- Neither detects carbon monoxide: you still need a certified CO alarm (EN 50291).
- Desktop design: both are made to stand on a table, desk, or shelf, so they need a flat surface.
The right sensor for each question.
Core CO₂ is built to answer "does this room need fresh air?", using a sensor that measures CO₂ directly, plus the temperature and humidity readings that help explain how a room feels. Core Max uses the same NDIR CO₂ sensor and adds laser particle sensing and gas sensing, for when cooking smoke, wood burners, new furniture, or decorating are on your mind too.
Real CO₂ readings, on a screen and on your phone.
Common questions.
How accurate are the readings?
On both monitors, CO₂ accuracy is ±(50 ppm + 5% of reading), so at a reading of 1,000 ppm, the result is within about ±100 ppm. Temperature is accurate to ±1°C and humidity to ±5% RH. On Core Max, particle readings are accurate to ±10 μg/m³ from 0 to 100 μg/m³, and ±10% from 100 to 500 μg/m³, and TVOC and formaldehyde readings are indicative.
Both are designed to help you understand how your home's conditions change, not to replace laboratory equipment.
What's the difference between NDIR CO₂ and eCO₂?
An NDIR sensor measures CO₂ itself, using the way CO₂ absorbs infrared light. eCO₂ is an estimate worked out from a gas (VOC) sensor, so it can jump with sprays and cooking even when the CO₂ level hasn't changed. Both Atmosense monitors use NDIR.
Why are TVOC and formaldehyde readings indicative?
Core Max measures them with a semiconductor gas sensor, which reacts to many gases at once rather than one gas alone. That makes it good at showing when levels rise and fall, for example after cleaning or decorating, rather than giving exact concentrations.
Do they work without Wi-Fi or the app?
Yes. Core CO₂ and Core Max both show live readings on their own display. To see readings away from home, view history graphs, and receive phone alerts, connect your monitor to the free Tuya Smart or Smart Life app. An app account is required.
How do the alerts work?
On Core CO₂, an audible alert sounds at 1,500 ppm by default, and you can change the alert level or switch the sound off in the app. On Core Max, each reading on the display is colour-coded green (Good), orange (Poor), or red (Unhealthy), so you can see which one needs attention.
With both, you can set your own push notification thresholds in the app.
Why does the reading change when I spray perfume or cook?
Perfume, alcohol, cleaning products, cooking fumes, and similar everyday sources can affect readings. Place your monitor away from where these are used, and look at trends over time rather than a single reading.
Is either monitor a carbon monoxide alarm?
No. Core CO₂ and Core Max measure carbon dioxide (CO₂). Carbon monoxide (CO) is a different gas: neither monitor detects it, and neither must ever be used in place of a certified carbon monoxide alarm (EN 50291).