Execution by electric chair is one of the most inhumane and barbaric forms of execution, hence why they got rid of it. They do not die instantly and feel excruciating pain. A lot of executions by the electric chair were botched - sometimes the inmate didn’t die with the first jolt of electricity so would have to have multiple. The inmate would often defecate and bleed because of the pressure of the expanding tissue. Their temperate becomes so hot that smoke would rise out of the body, and they would often receive third and fourth degree burns. Sometimes the eyeballs could pop out due to pressure. Afterwards, flesh could blister and fall off if touched. They are essentially being cooked alive.
Here it is described by US Justice Court William Brennan:
“…the prisoner’s eyeballs sometimes pop out and rest on [his] cheeks. The prisoner often defecates, urinates, and vomits blood and drool. The body turns bright red as its temperature rises, and the prisoner’s flesh swells and his skin stretches to the point of breaking. Sometimes the prisoner catches fire….Witnesses hear a loud and sustained sound like bacon frying, and the sickly sweet smell of burning flesh permeates the chamber. (Ecenbarger, 1994)”