Darth Vader tortured Luke's friends so that Luke, sensing their pain, would come to Cloud City. That's the trap. Vader needed a way to bring Luke to the Emperor so he decided to do carbon freezing. To ensure Luke would survive, the freezing was tested on Han Solo before Luke arrived, again this is before Luke arrived. Leia, Chewie, C-3PO, and Lando were all brought to the carbon freezing chamber when it was tested on Han. At this point Luke is not there yet. We even hear an imperial say during Han's freezing

OFFICER: Lord Vader, ship approaching - x-wing class

VADER: Good. Monitor Skywalker and allow him to land.

So Luke wasn't even there yet. While Luke was busy landing, everyone left the freezing chamber.

OFFICER: Skywalker has just landed, Lord.

VADER: Reset the chamber for Skywalker. ... See that he finds his way in here.

So everyone leaves the chamber but Vader, who waits in the chamber with the lights dimmed. Leia and Chewie leave with Lando (who later decides to free them instead of taking them to Vader's ship like Vader ordered). So Leia and Chewie leave with Lando. Han was on his way to Fett's ship when Luke, who had finally landed and entered the city, ran into them. They get away and Luke finds his way to the chamber. So, by the time Luke gets to the chamber, everyone has gone but Vader. Everyone certainly had enough time to leave the chamber while Luke was landing and disembarking.

Darth Vader tortured Luke's friends so that Luke, sensing their pain, would come to Cloud City. That's the trap. Vader needed a way to bring Luke to the Emperor so he decided to do carbon freezing. To ensure Luke would survive, the freezing was tested on Han Solo before Luke arrived, again this is before Luke arrived. Leia, Chewie, C-3PO, and Lando were all brought to the carbon freezing chamber when it was tested on Han. At this point Luke is not there yet. We even hear an imperial say during Han's freezing

OFFICER: Lord Vader, ship approaching - x-wing class

VADER: Good. Monitor Skywalker and allow him to land.

So Luke wasn't even there yet. While Luke was busy landing, everyone left the freezing chamber.

VADER: He's all yours, bounty hunter. Reset the chamber for Skywalker.

OFFICER: Skywalker has just landed, Lord.

VADER: Good. See to it that he finds his way in here. Calrissian, take the Princess and the Wookiee to my ship.

So everyone leaves the chamber but Vader, who waits in the chamber with the lights dimmed. Leia and Chewie leave with Lando (who later decides to free them instead of taking them to Vader's ship like Vader ordered). There are two main groups leaving; Leia, Chewie, and Lando etc. in one group, Fett and the now frozen Han Solo in another. Fett was taking Han to his ship when Luke, who had finally landed and entered the city, catches a glimpse of them. When Luke tries to follow them, Fett fires a few shots and they get away. Lando's group (with Leia and Chewie) are close by and hear the shots. Leia shouts to Luke that it's a trap. They also get away and Luke ends up finding his way to the carbon freezing chamber. 

So, by the time Luke gets to the chamber, everyone has gone but Vader. Everyone certainly had enough time to leave the chamber while Luke was landing and disembarking.

Darth Vader tortured Luke's friends so that Luke, sensing their pain, would come to Cloud City. That's the trap. Vader needed a way to bring Luke to the Emperor so he decided to do carbon freezing. To ensure Luke would survive, the freezing was tested on Han Solo before Luke arrived, again this is before Luke arrived. We even hear an imperial say during Han's freezing

OFFICER: Lord Vader, ship approaching - x-wing class

VADER: Good. Monitor Skywalker and allow him to land.

So Luke wasn't even there yet. While Luke was busy landing, everyone left the freezing chamber.

OFFICER: Skywalker has just landed, Lord.

VADER: Reset the chamber for Skywalker. ... See that he finds his way in here.

So everyone leaves the chamber but Vader, who waits in the chamber with the lights dimmed. Leia and Chewie leave with Lando. Han was on his way to Fett's ship when Luke, who had finally landed and entered the city, ran into them. They get away and Luke finds his way to the chamber. So by the time Luke gets to the chamber, everyone has gone but Vader. Everyone certainly had enough time to leave the chamber while Luke was landing and disembarking.

Darth Vader tortured Luke's friends so that Luke, sensing their pain, would come to Cloud City. That's the trap. Vader needed a way to bring Luke to the Emperor so he decided to do carbon freezing. To ensure Luke would survive, the freezing was tested on Han Solo before Luke arrived, again this is before Luke arrived. Leia, Chewie, C-3PO, and Lando were all brought to the carbon freezing chamber when it was tested on Han. At this point Luke is not there yet. We even hear an imperial say during Han's freezing

OFFICER: Lord Vader, ship approaching - x-wing class

VADER: Good. Monitor Skywalker and allow him to land.

So Luke wasn't even there yet. While Luke was busy landing, everyone left the freezing chamber.

OFFICER: Skywalker has just landed, Lord.

VADER: Reset the chamber for Skywalker. ... See that he finds his way in here.

So everyone leaves the chamber but Vader, who waits in the chamber with the lights dimmed. Leia and Chewie leave with Lando (who later decides to free them instead of taking them to Vader's ship like Vader ordered). So Leia and Chewie leave with Lando. Han was on his way to Fett's ship when Luke, who had finally landed and entered the city, ran into them. They get away and Luke finds his way to the chamber. So, by the time Luke gets to the chamber, everyone has gone but Vader. Everyone certainly had enough time to leave the chamber while Luke was landing and disembarking.