This question got me thinking whether the elevator shaft from the Emperor's throne room led all the way to the reactor core.
To borrow a quote from an answer in that question ...
When at last he reaches the open shaft he hurls the Emperor down into the reactor. It’s a long, long way down and the Emperor fires his lightning upward as he falls.
He might still have used his powers to save himself, but his hate is now so strong his only thought is to cause Vader more pain. So the lightning continues to flicker and flash even after the body is out of sight.
And then comes a great explosion when his body finally reaches the reactor and a poisonous wind races up the shaft, knocking Vader at last to the floor.
Beware the Power of the Dark Side!
There were spaceships flying around the reactor core so it must have been open to the vacuum of space. And the top of the elevator shaft ends in the Emperor's throne room, so it must have had air in it. Otherwise, how would Luke or the Emperor breathe? And if the bottom of the shaft was open to the reactor core, all the air would have rushed out to space.
Edit to add:
The movie shows the Millennium Falcon taking a few minutes to reach the reactor chamber, but Sidious dies just seconds after being thrown into the elevator shaft.
Did Darth Sidious fall all the way to the reactor core?