What is the lowest voltage that is usually considered hazardous to humans?

In electrical safety, 30 volts is generally recognized as the threshold where voltage becomes hazardous to humans. According to Ohm's Law, the current flowing through a body depends on both the voltage and the body's electrical resistance. While human skin normally provides some resistance, factors like sweat, wet hands, or a strong ground connection can drastically lower this resistance. Under these conditions, a voltage as low as 30 volts can push enough current (just a few milliamperes) through the body to cause a painful shock or even disrupt the heart rhythm. Higher voltages like 100V, 120V, or 240V are certainly deadly, but 30 volts is the starting point where standard safety precautions must be strictly observed in electronics.