NEC codes rate low voltage as anything below 30 volts. Voltage under this number is considered to be neither lethal or a significant danger. That being stated, it’s always smart to exercise care around anything that utilizes a 120volt source, which the system does. A dog or cat chewing through a wire would probably barely feel a shock, if at all. Although 12 volt is relatively safe with regard to harm to humans or animals, it still creates heat, can spark, and can cause fires.