Mold prevention with the AZ-Envy - Part 1

The following blog post was sent to us from the guest car Niklas Heinzel. Have fun reading and postponing:

The first part of this blog series is about the use of the Environmental Development Board AZ-Envy For early mold prevention in living rooms. We will first deal with the basics of mold prevention, as well as the technical approaches to solving this problem.

First, one should become aware of the health and financial damages of a mold from living rooms. Not only building substrate is infested, but man gets strongly felt the health consequences. Follow as a rhinitis (chronic nasal mucosal inflammation), an embodiment of type 1 allergies, asthma seizures and a generally increased probability to suffer from a respiratory disease are conceivable.

According to an investigation of the ESS (European Statistical System), an estimated 13.1% of the population in the 28 member states of the European Union lived in 2019 in an apartment with a continuous roof, moisture in thermal bridges or general rot. This statistic makes it very clear, even for Germany with 12% of the total population that the mold hazard is worryingly high in these buildings and thus a large mass of people of the EU would be exposed to a health-hazardous spore burden.

In addition, of course, an additional financial burden that can cost the analysis, elimination and rehabilitation of the growth site by a specialist company rapidly € 190 per sqm. Especially in advanced stages of growth, as this e.g. Hidden by furniture / favors, several square meters may be infested.

Source: Regine Szewzyk / Umweltbundesamt

Source: Regine Szewzyk / Umweltbundesamt

Some projects in the DIY area are probably more gambling as practical and applicable electronic circuits. Therefore, this project is concerned with a socially relevant topic with concrete practical benefit and should serve as suggestion to more inventions that can be used by society.

In order to develop an effective prevention agent at the end of this blog series, the basics are very crucial:

In the course of experts, a permanent fallow of a value of the relative humidity of ≤ 70% is recommended in order to avoid the formation of the most famous mold species. In living rooms according to the latest standard, but is a rel. Humidity of 40% The rule, especially to make the breathing air pleasant and comfortable.

The relative humidity indicates the saturation degree of air in percent (%). The lower the temperature, the less humidity, the air can absorb, d. H. With decreasing temperature, the relative humidity (with constant absolute humidity in G / m³) increases and vice versa. This means that with normal room air humidity already on colder areas the risk of mold formation without the training of tauwasser consists.

Professionals assume that spores will gain moisture from the ambient air during the germination and can only be absorbed from the building material after the formation of mycelium. A particularly growth accelerating effect also has the formation of dew, or condensation on surfaces.

In combination with the factor of the temperature, it becomes clear that with a longer-lasting internal air humidity of 60-65% is urgent to heat and to ventilate regularly. This is based on water transport when ventilating, as well as the temperature of the room air. Cold outside air, which enters the interior when venting into the interior, increases moisture when heated, which is removed to the outside with the heated air and can thus achieve dehydration even with rainy weather.

The colder the air, the more water you can absorb while heating. This effect can be explained by the fact that increasing the average speed of the molecules in the water and in space air increases with increasing temperature. Thus, from the water-containing water, more H2O molecules can be released from the liquid molecular bandage and go over into the air. Furthermore, it is recommended to open the windows in cross-flow ventilation, d. H. that one or more opposite windows are opened fully, so that across the house an air circulation can take place.

Problematizing the combination of poor air and heating behaviors, which requires a low temperature and a high humidity. In order to ensure comprehensive protection, I also used as an important supplementary factor the dew point temperature, which refers to the surface temperature, in which the condensate formation begins in the form of water on the walls. This moisture on the masonry represents the breeding ground for the mold. Therefore, it is called from the dew point temperature when combustion gases are saturated upon cooling with water vapor, that in the case of falling below the dew point temperature, the condensation of the water vapor begins. For a healthy living climate, warm room air should be a rel. Humidity of about 50% available. The dew point temperature is calculated as follows:

Calculation of the dew point temperature The calculated dew point temperature is the exact air temperature that must be undermined with unchanged pressure so that water vapor deposits as a dew or fog and the relative humidity is 100%.

This deposit is the breeding ground for mold and must be prevented, as well as in relation to the current room temperature (TI).

Thus, the structural basics would be collected, which serve as an approach to mold prevention. Therefore, in the technical discussion, it must be attempted to measure the room air temperature, the relative humidity (<65%) and the dew point temperature (

This is that AZ-ENVY development board Very well suited, because it offers all the features that are needed for our project. At this point again a small graph with the components of the board:

AZ Envy

First, there would be the MQ-2 gas sensor. This can output the changes in the composition of the room air based on an analog value calibrated on the outside air. No special gas is recognized as such, it can only be demonstrated an increased and possibly harmful concentration of gases H2, LPG, CH4, CO, alcohol, smoke and propane. The consideration behind it is the use as a room air quality sensor, which should animate a renewed ventilation interval.

To measure the important room air temperature and the relative humidity, the SHT30-DIS-B sensor should serve, despite its extremely small form factor of 2.35 x 2.35mm, both the relative humidity in% (± 1.5%) and the temperature in ° C (± 0.1 ° C) Extremely measure exactly and easily communicate with the ESP12-F via I2C.

With these sensors, we can not only measure room air temperature, relative humidity and dew point temperature, but also animate them to increased ventilation.

In preparation for part 2 of this blog, an AZ-Envy Board should be present, as well as an FTDI adapter for uploading the sketch to the ESP12F.

To program the board, under Tools, select the Board Generic ESP8266 and stay with the presets. After selecting the port to which you have connected your Envy, you can click Upload. After compiling the code and the initialization of upload, press the RESET and FLASH button in succession (pressing Reset) to put the ESP12-F into the flash mode. Then press the RESET button after the upload and the program starts. The following PIN configuration should be present between FTDI adapter and ESP12F:

FTDI adapter









Further information is also available in the already published blog AZ-ENVY - the slightly different micro controller board.


As a test for this configuration, it is important to first upload a small blink sketch, like this:

 void set up() {
   pinmode(LED_BUILTIN, OUTPUT); // Declaration of the LED port as output
 void loop() {
   digitalWrite(LED_BUILTIN, HIGH); // Lighting the LED in 1 second distance
   digitalwrite(LED_BUILTIN, Low);
How we use this sensor combination to use for the purpose of mold prevention, we will be considered in Part 2. We will look at the recording, processing (Arduino IDE) and storage of the measured values ​​(Google Firebase) based on the AZ-Envy Development Board.


Thanks to Niklas Heinzel for this blog post.

Esp-8266Projects for beginnersSensorsSmart home


Andreas Wolter

Andreas Wolter

Das Problem mit den zu nahe liegenden Sensoren ist mittlerweile bekannt. Niklas Heinzel wird im zweiten Teil darauf eingehen.

Andreas Wolter

Sven Linder

Sven Linder

My experience of this sensor is exactly the same as @Sebastian. The MQ2 sensor generates so much heat that it is impossible to get accurate temperature and humidity readings from the SHT30 sensor. The temperature readings will be off by at least 4 °C or so. And the humidity readings will be off by 8-10%.

veit burmester

veit burmester

Kann ich nur sagen drei Daumen hoch. Bin gespannt auf Teil 2



Ich habe vor einiger Zeit drei Envys gekauft und fand die Idee grundsätzlich super!

Leider stellte ich beim Experimentieren mit dem Board eine wahrscheinliche (Design-)Schwäche fest, die ich bisher nicht beheben konnte. Zum Beispiel wird die Temperatur durch den beheizten Gassensor so stark beeinflusst, dass sie – je nach Installationsort, Belüftung und Umgebungstemperatur – nahezu willkürlich erscheint. Damit ist auch die Feuchtemessung nutzlos.
Ich habe mit gedruckten Gehäusen, die die Bauteile gegeneinander abschirmten experimentiert, habe mit einem kleinen Lüfter einen Luftstrom erzeugt, habe versucht eine Fehlerkurve zu bestimmen. Aber leider bleiben alle meine Versuche, die Envys sinnvoll einsetzen zu können, erfolglos.

Aber vielleicht liegt der Fehler auch bei mir.
Wie gesagt: Ich finde die Idee toll! Und ich würde mich freuen, wenn Niklas mir in der Blog-Reihe zeigen könnte, wie es richtig geht oder wie man das Problem umgeht.

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