They say it has been tested and has a UL certificate.
It has a limited, small fuel supply, not continuous like gas or oil. Ethanol burns cleanly. IMHO, not too much chance of a problem if…the operator follows the instructions!!
I’ve seen some of these on different tv shows on Planet Green and DIY. Some of these units are BIG BUCKS. In the tens of thousands depending on the style. They are more of a mood setting / architectural type fireplace than one used for heating. The upper end ones sure look cool on tv.