Frequently asked questions about Oskar big

It may be that your external hygrometer and Oskar big are measuring different values because the devices are located in different positions (heights) in the room. Different humidity is measured depending on the airflow and temperature. A tolerance of +/- 5 % is normal depending on the type of device. Oskar big displays optimum humidity levels if he is positioned centrally in the room so that the room air can flow towards the sensor as freely as possible. If this is not possible, we would recommend positioning Oskar big on the wall with a clearance of at least 30 cm. Oskar big should never be “hidden” in the corner of the room or behind a sofa/piece of furniture as this may negatively affect the humidity measurement as well as humidification efficiency.

First check whether the float gauge (see A) can be moved up and down. It may be blocked due to too much limescale/dirt. Decalcify the water tank regularly to ensure trouble-free operation.

Oskar big consists of two parts: A top part and a bottom part. If the top part is not exactly in the right position on the bottom part, the float gauge sensor does not make contact with the electronics in the upper part. Position the upper part correctly to establish contact.

Should neither of these cases apply, lift off the upper part and clean the contacts (see B and C) with a damp cloth, dry them and place the upper part back on the bottom part.

After changing the filters, the LED for the filter change reminder does not turn off automatically. Press the reset button for 5 seconds (see A), until the blue LED is constantly illuminated again.

Set the hygrostat at the highest setting. The size of the room, the height of the room (2.5 m) and whether the room doors are closed plays a role. If the room doors are open, the adjacent rooms are also included in the total area. With a lower relative humidity (less than 35 %), the humidity will not increase immediately. This is because the floors, furniture and walls are the first to absorb the humidity before it ends up in the air. It can take up to two weeks for everything to have absorbed sufficient humidity and for the level in the air to increase. As long as you have to refill the water tank regularly, your Oskar big is functioning properly.

Yes, both filter versions can be used with Oskar big. We have recently updated the filter to a new version that works without the plastic frame. There are two reasons for this update: First, we were able to reduce the amount of waste by eliminating the plastic frame. The new filters are made out of textile- and plant-fibre. Second, the new material allows for a higher humidification performance.

In order to clean the inside, remove the filter cassettes and rinse out the water tank. Use a soft brush or a sponge to clean the tank thoroughly. Decalcify the water tank regularly depending on how hard your water it. Rinse out the water tank thoroughly after decalcifying and dry it before operating the air humidifier again.

Used filter casssettes have to be disposed of with regular household waste.

Dip the filter cassettes completely in water before the first use and then seep them a bit. Now you can put the filter cassettes in Oskar big and fit the upper part to the lower part.


For the hygienic and ideal operation of the air humidifier, the filter cassettes need to be replaced every two months. If the filter cassettes are used for a longer period the humidifying effect can be negatively impaired on the one hand and, on the other hand, the antibacterial action of the filter cassettes is no longer ensured. The filter cassettes can usually be obtained from where you purchased the unit.

A mild yellow or brown discolouration of the filter material, mainly in the upper section, is normal. The residual water needs to be emptied if you do not use Oskar big for some time. If the evaporator cassettes are submerged in water for a longer period of time, without the fan being operated, algal growth may occur or mould may appear. To prevent this from happening, empty the device and allow the filter cassettes time to dry. Refill the water again if Oskar big is used regularly.

The substances in tap water are the reason for the change in colour. The filter cassettes change colour faster depending the water quality. It does not look nice but it is harmless. If you haven’t used the filter cassettes for a long time, you can turn them over and continue using them. If the filter cassettes are older than two months, please exchange them for new ones (see question “How often do I need to replace the filter cassettes?”).

Please read the instructions on the label on the inside of the upper part of Oskar big. If your model has no label, this means you have an earlier model that can be cleaned with a vacuum cleaner or cleaned by a technician.

If you purchased your Oskar big before 2014, it must be switched on manually after the power supply is interrupted. The new models as of 2014 have a function where Oskar big switches back on automatically after the power supply is interrupted.

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