There are certain types of players for whom the less you say as a GM, the scarier the situation will be. The more stuff you specifically deny, the more the player will suspect that there's something hidden and dangerous going on that they can't detect.

This response can be cultivated. Never say, "There are no traps in the room," when you can say, "You don't detect any traps." Don't say, "There are no orcs around." Say, "There are no orcs visible within the range of the feeble flickering of your torches." And especially don't say, "It's perfectly safe to rest and regain your strength in the realm of the friendly elves. They tend to your wounds and give you delicious nuts and berries, and sweet honeyed wine to drink." Say instead, "The elves appear to be friendly, offering what they claim are healing balms and lotions. You sniff the golden liquid in a proffered cup, and think you can recognise a faint odour of almonds..."

Transcript

GM: R2, you're hidden amidst a pile of rubble.
R2-D2: Up periscope. Any threats?
GM: None... that you can see.
{beat}
R2-D2: ... Switch to infrared.
GM: No obviously abnormal heat signatures.
R2-D2: Hmm. Droids probably don't show up on IR.
GM: Really? Interesting.
R2-D2: Okay, what does that mean?
GM: I have no idea what you're talking about.
{beat}
R2-D2: I wobble to pick up parallax distortions from cloaking devices.
GM: How far are you prepared to move?
{beat}
R2-D2: I bolt out of the hangar bay at full speed.