Heat Sensor

The Heat Sensor is a treasure in, found in the Sightless Passage. It is actually a thermometer that reads "36.8° C", or 98.24° F, roughly the average human body temperature.

Collecting the treasure
It is completely buried in the northwestern room of sublevel 1 of the Sightless Passage. It can be located with the Treasure Gauge or Oatchi's sniffing abilities. It is hidden beneath a sizzling floor caused by a Pyroclasmic Slooch, meaning that Red Pikmin are essentially required to collect this treasure, although you can remove the floor with Oatchi if he has the Scorch Guard. To collect this treasure, you must first extinguish the sizzling floor, then throw 5 Pikmin in its vicinity. It is recommended to also defeat the other Pyroclasmic Slooch nearby.