There are several key safety considerations involved with the building and operation of a fusor. First, there is the high-voltage involved. Second, there are the x-ray and neutron emissions that are possible. Also there are the publicity / misinformation considerations with local and regulatory authorities.
Ah, I remember reading this when it first came out! I thought it was the coolest thing ever.
Still do.
(Since I was curious)
https://en.wikipedia.org/wiki/Fusor#Safety