There's no air out in space. If that door would open now, it would pull all the air out of this room and us with it.
10 seconds sound clip from the Santa Claus Conquers the Martians (1964) movie soundboard.
You can hear this line at 00:47:11 in the Blu-ray version of the movie.
Quote context
[...]
- When it reaches the pressure of the rest of the ship, you can take your space suit off.
- Well, where's the control that opens the door?
- Not here. That's in the control deck.
- You see, once you pull that switch, the warning bell sounds, and in 60 seconds, that door opens.
- That's to give the spaceman a chance to make a final check on their equipment.
- You certainly know a great deal about space travel, son.
- He wants to be a spacemen when he grows up.
- 60 seconds. That must be the door timer.
[...]