X10 is not suitable for any safety related use.
Having lived with it for quite a while, I'm not sure it's really
suitable for any use. Even counting the trouble of doing so, I'd much
rather run class 2 control wiring and use solid-state relays (or even
electromechanical relays).
Okay, that's a bit of an overstatement, but not by all that much. The
only real advantage I see to X10 is that it's something that an
electrical-ignorant end-user can use as an aftermarket add-on without
too much trouble or risk.
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse(a)rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B