A plethora of answers and the movie itself reveal that children are in fact non-toxic for monsters.

Let's see: enter image description here

In this scene, right after the conversation with Waternoose is concluded, Mike and Sully walk away. At this point a CDA worker points his/her geiger-counterish device to our heroes, and the device actually gives a warning, but a passerby gets jumped, and the scene ends.

So if the children are non-toxic, what kind of energy does this said device detect?

  • 5
    I don't see why there would be a connection between the (false) proposition that humans are toxic to monsters and the (true) proposition that humans can be detected by a device. They seem like two entirely different things.
    – wyvern
    Commented Apr 18, 2016 at 22:58
  • Two entirely different things ask a very simple question: CDA, the company run by the toxicity lie, can detect a human being. If the detected energy isn't related to toxicity, then what is it?
    – VerpinZal
    Commented Apr 18, 2016 at 23:03
  • @VerpinZal latent scream or laughter energy?
    – Moo
    Commented Apr 19, 2016 at 10:36

2 Answers 2


So a bit of conjecture but I think it's reasonable

Children screaming or laughing is considered an energy source in the movie. Presumably, a child simply breating normally would produce some amount of energy. Consider Randall's Scream Extractor. You can't scream with a vacuum hooked to your mouth so it would logically convert the breathing of the child to energy. So it would make sense that a child detector would detect the (faint) primary source of energy in Monstropolis.


Pure conjecture warning!

We know that the Monster City is dramatically struggling for sources of energy, to the point that they're forced to rely on scream energy to power their home appliances. Despite their advanced technology, they seem to lack the ability to generate electricity from the most obvious source of power available to a high-tech society; nuclear fission. Why? Because the monster world has ultra-low levels of background radiation and practically no high radiation sources.

So what are the "geiger counters" detecting?

They most obvious solution is that the child detectors are detecting what geiger counters usually detect; radiation. In a world with practically no background radioactivity, the perfect way to detect an intruder from the human world (such as a human child) would be to look for radiation spikes that are out of the ordinary and to follow those. Note how the detector jumps each time it's pointed at someone who's spent time on the Scare Floor. Clearly exposure to Human World air has increased their overall radioactivity...


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