Yes, but only in areas where you are not naked.
The starting point is that there should be no camera surveillance in areas where sauna visitors may be naked. This includes changing rooms, shower rooms, toilets, swimming pools and hot tubs, saunas and the areas where visitors enter and leave the saunas.
Filming people who are naked is a major invasion of their privacy. The balance between the interests of the sauna and those of the visitor should under normal circumstances always be in the visitor’s favour. After all, they must be able to assume that they will not be observed in such a place. That is paramount.
In addition, the sauna can also achieve the purpose in other ways. This purpose is often security or the prevention of (undesirable) intimacies. This can also be achieved by, for example, having personnel, whether recognisable as such or not, walk around regularly.