Air quality monitoring – Micro-sensor based solution
Downloads & FAQ

Cairnet® mini-station


Cairnet® is a real-time standalone and networkable air-monitoring station including up to six Cairsens® micro-sensors. It provides cellular communication within a waterproof housing. The most common types of pollutants monitored are:

  • H2S/CH4S, NH3, nmVOC, O3 + NO2, NO2, CO, SO2, PM10, PM2.5 & PM1.

It is a modular station featuring up to six sensors and compatible with an optional weather station.

Cairnet® can be powered by solar panels or main AC / 12 or 18 VDC power supply. The autonomous operation is available by using rechargeable battery (included with Cairnet®) and the solar panels.


Yes, it is possible to activate the stations without technical support. The Cairnet® stations are preconfigured, all you have to do is insert the SIM card, fill in the information related to the SIM card used (APN-Users-Password) and put it into operation. Measured data will be available in your Caircloud® account within approx. 15 minutes.

Yes, it is completely Plug & Play and IoT ready for data transmission into the cloud. The detection & linking of the Cairsens® micro-sensors / Cairnet® / Caircloud® is automated. No cables or complicated installation is needed, you just need to insert your SIM card.

The Cairnet® mini-station is shipped with its mounting kit, it is easy to install (less than 5 minutes) and to move around.

The guaranteed lifetime of the Cairnet® housing and its components is 5 years.

The Cairnet® housing requires only annual maintenance when sensors should be replaced, that is after 1 year of use.

Yes, Cairsens® micro-sensors should be replaced after 1 year of use.

Upon reception of the new Cairsens®, disconnect the old ones from Cairnet®, connect the new Cairsens® and return us the old Cairsens® along with the Return Material Authorisation (RMA) form sent by our Customer Service or to be requested via the technical support interface on our website.
They will be included in a recycling program.

No further intervention is required beyond a simple check of the cleanliness of the solar panels. Maintenance status is monitored directly from the Caircloud® thanks to the feature "tracking state of life of the Cairnet®". This allows advanced remote diagnosis of various elements such as the solar panels power.
Cairsens® are manufactured in France by ENVEA and calibrated in our metrological laboratory using Standard Reference AQMS monitors. Every sensor shipped includes a calibration certificate. No maintenance nor recalibration is needed within the 1-year warranty period.

Data & communication:

Cairnet® uses 2G, 3G, 4G and 5G cellular communication. It requires a 3FF type SIM card (not provided), and a data volume of 500 MB per Cairnet® and per month. Data are transmitted to a secured cloud database and are accessible with the private & secured web access interface of the Caircloud®. An FTP export or API protocol allows the export of data to an external database.

No, the data can be retrieved in 2 ways:
Firstly, in the Cairsens® itself. Data are saved in the micro-sensor and are accessible via Cairsoft. Secondly, when the cellular communication becomes available again, Cairnet® will automatically resend up to 3 days’s data that was not sent during the signal outage. Data are therefore available in Caircloud®.


The price depends on the pollutants to be measured. Please contact us for quotation.

Please contact us for renewal quotation.

Caircloud® – Data Acquisition and Handling

Yes, Cairnet® sends the 1-minute averaging data of all embedded micro-sensors to the Caircloud® database. The transfer frequency can be set trough Caircloud® interface. It is by default set to 15 minutes.

Yes, the subscription is valid for one year and is renewable by tacit agreement. If it is not renewed, the concerned account will be closed and the data will be lost.

There is no limit.

Yes, Caircloud® is a fully secured web-based interface, it can be accessed via any PC, smartphone, tablet, etc.

Yes, the database is hosted on our servers and the data is only accessible by the user with secured access credentials.

Yes. It is possible by using FTP server Export or API Rest protocol.

It’s possible to retrieve data from Cairnet® (AC powered version) via ethernet connection (Modbus TCP-IP).

Yes, the micro-sensors measurement data are available directly in Caircloud®.

Cairsens® micro-sensors

Power supply and operations:

Cairsens® micro-sensors have no battery inside. For standalone operation they need to be connected to an external battery (5VdC USB power supply). These external batteries must be the "always-on" type which allows to power systems with very low consumption. Cairsens® can be externally powered by the mini-USB or micro-USB connector.

Example of an “always-on” type Power Bank available on the market:

Other models, available directly from the manufacturer, can offer last up to 50 days in continuous operation:
  1. Model V75 USB Battery Pack 50 day’s autonomy
  2. V50 USB Battery Pack 30 day’s autonomy

It is 15 mA at 5 VDC.

Cairsens® are manufactured in France and calibrated in our metrological laboratory using Standard Reference air quality monitors. Every sensor shipped includes a calibration certificate guaranteeing accurate measurements during one year of use.

Turn on the Cairsens® by powering it. A period of 24 hours, in operation, is required to obtain the stability of the measurement.
Please follow the instructions in the operating instructions manual.

Cairsens® are calibrated before shipment on the whole range of measurement from min (ca. 0 ppb) to max. The information is stated in the certificate that comes with every sensor. Indoor environment can produce chemical reaction of the sensor and eventually a signal offset. Other items to check and that could be a reason for the high measurement level are:

  • The power connection is not working
  • Potential obturation of the inlet airflow
  • When used for the 1st time, the sensor needs 24h operation before using the data. Please follow the instructions in the operating instructions manual.

The very first version of Cairsens® sensors have offered the possibility to retrieve the temperature and humidity, but only for Research and Development purposes, with no specification or characteristic being communicated either in the brochures or in the specification sheets. As it has generated confusion and misinterpretation, that feature has been removed in the current Cairsens® versions.

Cairsens® lifetime is one year of use and shall be replaced after this period.

Cairsens®’lifetime is one year of use and shall be replaced after this period.

Cairsens display:

There could be several reasons to this:

  • The power level of the external battery might be low.
  • The sensor doesn’t detect any pollutant, check and move the sensor to another measuring area.
  • The measuring cell no longer reacts: Contact technical support.

The values on the screen (sliding 1-minute average) are refreshed every 10 seconds while those in the memory (sliding 1-minute average) are saved by period of 1 minute (or 15 minutes following the selection made).

The measurement:

The 1-minute moving average is calculated on 7 acquisitions per second, on which the median is taken to obtain the average minute.

All previous stored data will be deleted.

The maximum backup period is 20 days with the 1-minute measurement interval. When the memory is full, the oldest data will be deleted and replaced by the latest ones.

The conversion factor is 1.42 at 20°C For information, here are the factors for others gaseous parameters at 20°C:

  • SO2 1 ppb = 2.62 µg.m-3
  • NO2 1 ppb = 1.88 µg.m-3
  • O3 1 ppb = 2 µg.m-3
  • CO 1 ppb = 1.145 µg.m-3
  • NH3 1 ppb = 0.71 µg.m-3

The conversion factor is 1 ppb = 2 µg.m-3 at 20 °C

Yes, even connected to the power supply (PC or sector) Cairsens® continues to measure and save data.

NO2, O3 + NO2, SO2, CO, H2S/CH4S, nmVOC, NH3 and PM10/PM2.5/PM1.

Cairsens® measures one parameter at a time for gaseous pollutants. However, PM Cairsens® measures 3 parameters (PM1, PM2.5 and P10) simultaneously.

Electrochemical for gases, PID for nmVOCs and Laser Light Scattering for PM.

Please download the Cairsens® calibration advice note. Cairsens® is considered as a detector and gives an indicative measurement following the requirement of Directive 2008/50/EC for the indicators systems.

It is not a reference system and can’t be compared or assimilated to it. However, ENVEA’s main objective is to provide precise and reliable measurements of pollutants. That’s why Cairsens® are calibrated thanks to AQMS reference analyzers and with the same quality and the same production procedure as those applied to ENVEA’s instruments. Moreover, each Cairsens® micro-sensor comes with an individual calibration certificate.

That allows Cairsens® to be used upon reception (respecting the conditions of use described in the user manual). The micro-sensor can operate 1 year without any recalibration. After that period of time, it’s recommended to replace the Cairsens®.

Cairsens® are calibrated for the targeted pollutants. Regarding the cross sensitivity, please refer to the technical specifications available on our website.

Each Cairsens® is calibrated by using an AQMS reference analyzer. Several concentrations covering the full measuring range of the Cairsens® from 0 to the maximum range value are done. Then validation of each measurement level is performed with an accuracy of ±30% as it is required by the directive 2008/50/EC.

Cairsens® provides a measurement with an accuracy of ±30% from the target as required by the directive 2008/50/EC (when respecting the using conditions described in the user’s manual and the technical specifications).

No adjustment is needed, see answer to previous question.

The measurement is carried out by the Cairsens® which has its own dynamic sampling system (using a micro-fan). Therefore, whether the Cairsens® is embedded into a Cairnet® or not, measurement is done by the micro-sensor itself.

In order to check the measurement of the Cairsens® individually, please download the verification prerequisites note.

Measurement accuracy is guaranteed for 12 months of use plus 3 months storage time (under storage condition listed in the user guide). During this 12-month period of use, the ageing of the sensor is compensated by the Cairsens®.

The lifetime is one year plus 3 months storage time (under storage condition listed in the user guide). Beyond this period, Cairsens® will continue to deliver a signal, but the measurements are no longer certified within ±30% as required. Therefore, it is recommended to replace the sensor by a new one to continue to have reliable and accurate measurements.

Yes, see answer to the question 1 of the Cairsens® section.

The identified compounds that could interfere are listed in the spec sheet.

Cairsens® micro-sensors are manufactured by ENVEA. They feature electrochemical cells for most of gases, PID (Ionization potential 10.6eV) for nmVOC and laser scattering light for our latest particulate matter (PM) Cairsens®.

The measurements done by the Cairsens® micro-sensors have a resolution of 1 ppb with 1-minute sliding average. Detection limit goes from 10 ppb for some micro-sensors (H2S range 0-1000 ppb for example) to 500 ppb for the others (NH3 or nmVOC range 0 to 16 ppm for example).

The Cairsens® NO22 is based on a O3 filter and dedicated to measure only NO2. Regarding the possible interference: we could mention CL2 and H2S. Please check the specification sheet for further details.


The new Cairsens® are both USB and UART compatible.

Yes, it is possible to do so. For the USB protocol, please refer to the user manual of the Cairsens®.

UART or Modbus communication through micro-USB connector.

Cairsens® itself does not feature wireless communication. We recommend it to be used with Cairnet® station that is designed for autonomous operations and include wireless communication.

The Cairsens® V3 micro-sensor is compatible with the previous versions of Cairnet®. The compatibility is operated thanks to the mini-USB port.