The CO2 reading on a Tuya TS0601_air_quality_sensor can stay flat or follow the VOC reading instead of changes in the room. Zigbee2MQTT documents the reason: this model has no CO2 sensor. Its reported CO2 value appears to be calculated from VOC, so a calibration offset cannot turn it into a real CO2 measurement.
The findings here come from device documentation and owner reports. They are not measurements from a unit tested for this article.
This covers the Zigbee variant Zigbee2MQTT identifies as TS0601_air_quality_sensor. TS0601 is a generic Tuya model ID shared across unrelated device types, including Tuya’s TS0601 curtain motors, which have nothing to do with air quality. Zigbee2MQTT also lists other Tuya air-box model IDs (TS0601_airbox, TS0601_smart_air_house_keeper, TS0601_co2_sensor); the no-CO2-sensor finding here is documented for TS0601_air_quality_sensor specifically, so check which page your unit maps to. If Zigbee2MQTT doesn’t recognize your unit at all, see writing a converter for an unsupported TS0601 device.
The symptom: a CO2 number that doesn’t follow the room
Owners describe a CO2 reading that barely changes as people enter a room, or one that rises and falls with VOC. Those observations fit Zigbee2MQTT’s warning about calculated CO2, although the behaviour of an individual unit still needs checking.
What the sensor actually measures
Zigbee2MQTT exposes temperature, humidity, CO2, VOC, and formaldehyde for this model, with calibration offsets. Temperature and humidity also have precision settings. An exposed value tells you what the firmware reports; it does not prove that a separate sensor measures it.
temperature humidity voc co2 # reported value; no dedicated CO2 sensor formaldehyd # Zigbee2MQTT property name; measurement method not established here
The CO2 warning is explicit in the device documentation. Formaldehyde is less clear: the page lists the value but does not explain its measurement method. Owners in the discussion below describe a single gas sensor. That report raises questions about the formaldehyde figure, but it is not enough to establish how every rebranded unit produces it.
The device page says it plainly
The Zigbee2MQTT device page warns that the CO2 value does not agree with a real CO2 sensor. It also notes frequent updates that can put a significant load on the Zigbee network. Accuracy and message volume are separate reasons to be cautious about this model.
Community reports say the same thing, years apart
The May 2021 device-support discussion includes owners describing estimated CO2 and roughly 4–10 MQTT messages per second. These are reports from their units, rather than a specification for every box sold under the same name.
A 2022 AirBox04 issue reported swapped CO2 and formaldehyde values. Other historical reports questioned units. Mapping bugs are separate from the lack of a dedicated CO2 sensor, and an old issue should not be read as the current converter’s behaviour.
A Home Assistant Community discussion includes a comparison with a reference CO2 sensor in which the Tuya unit failed to follow changes in room CO2. Such comparisons support the warning about this device; they do not establish the hardware inside every newer Tuya air-quality product.
Does that make it useless?
It may still provide temperature, humidity, and a rough indication of changes detected by its gas sensor. The useful question is whether those readings behave consistently enough for your intended use.
| Sensor type | What it actually measures | CO2 reading | Good for |
|---|---|---|---|
| Tuya TS0601_air_quality_sensor | Reported VOC, temperature, and humidity | No CO2 sensor; value appears derived from VOC and doesn’t match a reference | A supplementary indication of changing air conditions |
| Dedicated CO2 sensor (e.g. SCD30-class NDIR) | Dedicated infrared CO2 sensor | Directly measured | CO2 monitoring and ventilation decisions that need real numbers |
A VOC trend may help trigger a fan or a reminder after cooking or cleaning, but it cannot tell you whether CO2 is high. Check that the reading responds sensibly before using it in an automation. If VOC is all you need, our Aqara TVOC monitor setup guide covers a device sold for that purpose without an extra CO2 figure.
Do not use this device’s CO2 number for thresholds that require measured CO2, occupancy estimates, or health decisions. Use a dedicated CO2 sensor for those purposes.
What to buy instead, if you need real CO2 data
For measured CO2, choose hardware with a dedicated sensing element and published specifications. NDIR is a common approach, though it is not the only direct CO2 sensing technology. Check the exact sensor and its calibration requirements rather than relying on “CO2” in a listing title.
The other cost: update flood on your Zigbee network
Frequent reporting can also make this device a poor fit for a busy mesh. Our guide to Zigbee2MQTT debounce and throttle options explains how to reduce MQTT publications. Those settings act after Zigbee messages arrive; they do not stop the sensor transmitting over the radio.
FAQ
Does the Tuya air quality sensor really measure CO2?
No. Zigbee2MQTT’s device page states it exposes a CO2 value but has no CO2 sensor; the number appears to be calculated from the VOC reading.
Why is my Tuya CO2 reading always close to VOC? The device documentation says CO2 appears to be calculated from VOC. Similar movement in both readings is consistent with that explanation.
Is the Tuya TS0601 air quality sensor accurate? Its CO2 value is unsuitable for measuring real CO2. This article does not establish the accuracy of VOC, temperature, humidity, or formaldehyde; those need their own reference comparisons.
What does “calculated CO2” mean? The firmware reports a CO2-labelled value without a dedicated CO2 sensor. Zigbee2MQTT says it appears to come from VOC.
Should I trust a cheap Zigbee CO2 sensor for ventilation decisions? Price alone does not answer that. For this particular model, the documented lack of a CO2 sensor rules out decisions based on its CO2 number.
Limits of the available evidence
The device page establishes the exposed values, the CO2 warning, and the high update rate. The linked owner discussions add comparisons and observations about particular units.
The formaldehyde sensing method remains uncertain. Reports of a single gas sensor are a reason to investigate, not a substitute for a teardown or reference measurement.
No replacement model is recommended here, and no side-by-side test was performed for this article. If you already own the device, comparing its readings with a suitable reference will tell you more than adjusting offsets until the numbers look plausible.
These readings can still reach Home Assistant locally through Zigbee2MQTT. Local transport does not make them more accurate. See what stays local when a Tuya device is blocked from the internet and reported humidity problems with the TS0201 for related limitations.