Instant Pot’s steam release handle is a safety device. Just like conventional pressure cookers, the steam release handle works simply by weight pressing on the steam release pipe. Since the contact between the steam release handle and the pipe is not fully sealed, traceable steam may sometimes be seen during normal working conditions.
Instant Pot’s steam release handle has a pressure rating of 105kpa or 15.22psi. The steam release handle keeps the working pressure always under the specified pressure rating.
Instant Pot’s pressure sensor is at the bottom under the heating element. The pressure sensor works by measuring the force pressing down on it, including the weight of food. When there’s small amount of food (under the 2 mark on the inner pot), the pressure sensor is slower at turning off the heat. Because of that, the momentum of the heat can push the pressure over the specified pressure rating, which causes a small amount of leaking from the steam release handle. Once the heating momentum is over, the pressure will be kept at the working pressure well under the 105kpa (15.22psi), and only minimal steam will come out of the steam release handle. This is still perfectly safe. Please see the illustration of Instant Pot working pressure diagram to understand the pressure changes over a cooking cycle.
Normally, if the food is over the “3” mark in the inner pot, there’s only minor traceable amounts of steam coming out of the steam release handle.