There are fire hazards with Any electrical device if not used properly.
Its pretty easy to prevent a fire, its common sense, Dont use anything that is damaged, Dont use run your ballast if it ever got water on it or anything like that. Never run it with frayed wires, make sure you Bulb is not cracked or defected, run a test before leaving it unattended.
Dont Ever try to wire anything, or set up anything you are unsure of. Do your Research.
Other then the actual lighting sytem there could be faults in the actual house, the existing wiring could be old, the breakers might not be able to handle the load, the only way its going to cause a problem is if you were to overload the circuit. Always check the breakers, average house will run on 15 amp breakers for standard outlets. A 1000w HPS ballast pulls 5-9 amps, so a 15 amp house breaker could handle only 1 x 1000w hps, if you added 2, it would overload the circuit and Probably just cause the breaker to flip.
If nyou run everying on separate suitable breakers, or have an electrition upgrade your system then you really have nothing to worry about.
Most people, including myself, dont worry too much about it because as long as you dont overload the circuit breakers you should be fine.
In Any situation if your unsure do some research. Theres a reason you dont hear about growops burning down all the time, it doesnt happen very often because most gorwers are pretty meticulous in getting there grow room set up Perfect.