Ventilation thermo hygrometer

When does room ventilation to achieve the right humidity make sense?

The new BEL-AIR can answer this question for you by simultaneously measuring the values of temperature and humidity in the room and outdoors.

This is a question that is often asked today, especially because of the problem of mold, and the answer to which is not always easy even for an expert or trained weather observer. With the digital combi-meter BEL-AIR, this question is continuously answered via the display.

Particularly in historical church rooms, the reduced heating activity causes over-humidification of the room air and thus moisture precipitation on cold surfaces, e.g. walls or organ parts. Together with a layer of dust, these are optimal breeding grounds for the mold spores that are always present in the air of the room. The result is visible mold coating. The formation of mold can be counteracted by preventing this over-humidification of the air in the room through timely ventilation under appropriate outdoor conditions. The BEL-AIR is a great and inexpensive help for this, so that you can open or possibly close the windows at the right time. Because of the often insufficient ventilation possibilities in historical churches, the installation of electric exhaust fans should also be considered. Normal bath ventilators cause already in large rooms a meaningful exhaust air. Installed at possibly existing ceiling holes, too humid room air can thus be discharged into the attic area at certain times.

The combination device consists of a comfortable indoor thermohygrometer with a large digital display for the indoor values and a receiver for the wireless outdoor sensor with a range of up to 100 meters. Furthermore, the digital display provides you with the appropriate information for your ventilation behavior.

From the indoor and outdoor values, the device calculates the resulting change in humidity in the interior and gives you the following information by means of 5 display fields: Center: "No change" No change necessary Left RED: "More wet" When ventilating, it becomes more humid in the room Right GREEN: "More dry" When ventilating, it becomes drier in the room Left outside: Absolutely ventilate - open window (only displayed if necessary) Right outside: DO NOT ventilate - keep window closed (only displayed if necessary) Furthermore, the display has an optical pointer that signals the current humidity level to you.

Dimensions: Indoor unit with display 160 x 95 x 20 mm Outdoor sensor 100 x 40 x 25

Batteries: 2 pcs. AAA 1,5 V each included in delivery 4 pcs. batteries!

Delivery indoor and outdoor unit incl. batteries for both devices!

Please note that extensive advice on the special use of these devices for end users is not included in the device price. Specialists on site, such as climate consultants, organ builders, organ experts, will charge for their consulting work according to time spent.

When mounting the outdoor sensor, make sure that it is mounted on the north side of the building and in a place without direct sunlight for correct measurement.

If you are looking for a general overview of different hand-held meters, please click here. If you are looking for a general overview of different hand-held instruments, please click on the following link thermo-hygrometers and different hand-held instruments in our digital catalog. Handheld meters.

We also carry liquids for the treatment of mold on walls and objects. Please click on Fungoproducts for more information.


Observation from practice

In the photo you can see the display on a midsummer day in the morning. By gut feeling, you would say that you let the even cooler outside air into the room.

However, the meter asks you to keep the windows closed, because the rel. humidity outside is very high and opening the windows would lower the temperature in the room, but the rel. humidity in the room would continue to rise. Overhumidification of the room with the subsequent storage of moisture in the walls over time would be the basis for developing mold.

Click on the photo to enlarge it.

Product variants
Part number
Net price
Gross price
BEL-AIR ventilation thermo/hygrometer digital indoor and outdoor without batteries
37,50 €
44,63 €
BEL-AIR Lüftungs- Thermo/Hygrometer digital innen und außen ohne Batterien - Einzelpreis bei Mengenabnahme ab 3 Stück -
32,50 €
38,68 €