This is UV-C radiation and light of this wavelength (which is emitted by low pressure mecury lamps) can indeed be used for disinfection purposes. The nucleic acids (DNA and RNA) has an absorption maximum for UVC radiation at 265nm, causing DNA/RNA damage. The radiation of the mercury lamps is only a little below, making them still quite effective (see the image from here):
This is used in "Ultraviolett germicidal irradiation" for example in water disinfection systems or also for workplaces. The problem with this irradiation is that it causes severe sunburns (and very fast) and also causes plastic materials to decompose (like leaving them in sunlight but much faster). Since I know the precautions for using such devices at workplaces, I wouldn't consider them safe for home use.
The other problem is that you need a pretty clean area for the radiation to be effective. We have to clean our work benches for doing cell culture work entirely so that no shadows are cast in which the UV radiation wouldn't be working since the area is shielded. Imagine this for your home. Additionally I think the fear for germs at home is massively overrated and that there is not need for theses devices at home.