What is the minimum current level that can be dangerous if sustained?

• A. 20 mA
• B. 5 mA
• C. 100 mA
• D. 1 A

Answer: (A)

The current needed to pose serious risk depends on how long it lasts. Very small currents are just a tingling sensation and rarely cause harm if they don’t persist. Once current reaches around 10 to 20 milliamps with AC, the body can experience a strong muscle contraction that makes it hard to let go of the source. If the current path goes through the chest, that sustained exposure increases the chance of heart rhythm problems. Because harm from electrical exposure is a function of both magnitude and duration, this level—about 20 milliamps—represents the smallest current that can be dangerous if it remains for even a short period. Higher currents (like 100 milliamps or more) are certainly dangerous, but they’re not the minimum threshold for danger.