What is the lowest current that has the potential to cause a fatality from a 110 volt power source?

The lowest current that has the potential to cause a fatality from a 110 volt power source is indeed identified as 15 milliamperes. This is primarily due to the physiological effects of electric shock on the human body.

When exposed to electrical current, particularly in the range of just a few milliamperes, a person can experience muscle contractions, respiratory issues, and disruptions to the heart's normal rhythm. Specifically, currents as low as 10 to 30 milliamperes can lead to ventricular fibrillation, which is a potentially lethal condition where the heart quivers instead of effectively pumping blood.

The selection of 15 milliamperes reflects a recognized threshold where the risk of fatality becomes significant. This contrasts with higher amperages which, while still extremely dangerous, are above this critical threshold where immediate cardiac effects typically occur. Therefore, understanding the implications of current flow through the human body is key in electrical safety practices, particularly in environments like laboratories where such exposures may happen.