Exposure to an electric current of how many milliamperes can be fatal if it lasts for one second or more?

An exposure to an electric current of 100 to 200 milliamperes (mA) can indeed be fatal if it lasts for one second or more. This range of current is significant because it is well above the threshold of what humans can typically tolerate without experiencing severe physiological effects. Currents in this range can cause ventricular fibrillation, which is a life-threatening condition where the heart quivers ineffectively instead of pumping blood.

Understanding the impacts of electrical current on the human body is crucial, particularly in fields related to HVAC and electrical work, where technicians may encounter situations with live wiring or equipment. While lower levels of current can cause discomfort, muscle contractions, or other harmful physiological responses, the 100 to 200 mA range poses a serious risk of fatal arrhythmias and requires immediate medical attention if exposure occurs.

The higher ranges, such as 200 to 300 mA or above, would likely lead to even more severe outcomes, but the specified range of 100 to 200 mA marks a critical threshold where the probability of fatal effects becomes significantly heightened.