RPGMemes

When the party enters the room and you describe what they see, just casually say "You don't see any traps".

That's usually enough.

I once ran a Dread campaign where the players were a group of tourists on a tour through a stalactite cavern. When they reached the deepest point of the tour, they heard an explosion from the entrance and the lights went out. As soon as the lights were out, someone (a disgruntled former employee of the stalactite cavern tour company) killed the tour guide with a crossbow.

The players then had to make their way through the long-abandoned and partially flooded other exit of the cavern.

I gave the killer a heavy, wheezing cough, so any time they spent too long discussing things, I would just cough. That was enough to bring the tension way up again.