Hygrostats

Humidity sensors for ventilation track the air humidity level in the room and independently start the fan when the indicator exceeds the set threshold. A person does not need to turn anything on manually – the system reacts to changing conditions automatically.

A bathroom or windowless toilet suffers the most from condensation and moisture exactly when no one has time to manually turn on the fan in time – during or immediately after a shower. An automatic solution to this problem has existed for a long time and is relatively inexpensive.

This is especially relevant for rented apartments or office spaces, where tenants or employees simply forget about ventilation until the moisture starts damaging the wall and ceiling finishes, and mold appears in the grout between tiles and at the joints. 

How air humidity sensors work

The operating principle is based on continuous humidity measurement and comparing the current value with a pre-set trigger threshold.

• the sensor detects a rise in humidity above the set level;
• the humidity controller sends a signal to start the fan;
• the equipment operates until the indicator returns to normal;
• after reaching the normal level, the system automatically turns off the fan.

Parts for ventilation systems of this type are usually mounted directly near the fan or integrated into its housing, depending on the specific equipment model.

The turn-off delay time is also configured separately – this allows the system to run for a few more minutes after the humidity has formally returned to normal, ensuring more thorough drying of surfaces.

Hygrostats as a separate type of controller

These devices differ from standard humidity sensors by having a mechanical trigger threshold adjuster, which the user configures independently for the specific conditions of the room. Ventilation electronics in such devices is simpler compared to fully automatic models. This approach is convenient because the humidity threshold can be quickly adjusted without reflashing or complex configurations via additional devices.

Where a hygrostat can be installed

Most often, the equipment is installed in rooms with a high risk of condensation and moisture accumulation throughout the day.

• bathrooms without natural ventilation;
• toilets with shower cabins;
• basement rooms with consistently high humidity;
• technical rooms with equipment sensitive to condensation.

The sensor's location also affects reading accuracy: mounting it too close to a steam source can lead to premature system triggering. The optimal distance is usually specified in the manufacturer's instructions and depends on the specific sensor model, so it is worth checking this parameter before installation rather than relying on approximate visual estimates.

Types of sensors depending on the task

A general-purpose air humidity sensor is suitable for most residential spaces, while specialized models are designed for specific operating conditions.

A humidity sensor for a fan should be selected separately, taking into account the connection type – wired or wireless, as well as compatibility with the specific brand of equipment to which the device will be connected.

Condensation on walls and ceilings is the main visual indicator that the existing ventilation is insufficient and it is worth considering the installation of an automatic sensor instead of manual control.

How to choose and buy in Ukraine

Before buying a humidity sensor, it is worth determining the room type and the desired control method – automatic triggering at a humidity threshold or manual adjustment via a hygrostat.

• check compatibility with the existing fan model;
• determine the optimal trigger threshold for the specific room;
• pay attention to the mounting type – wall-mounted or built into the housing;
• clarify if additional electronics are needed for connection.

A properly selected sensor starts the fan exactly when it is really needed, without wasting electricity on continuous equipment operation. The payback period for such a solution is usually a few months due to electricity savings and a reduced risk of moisture damage to the room's finishes.