It could be because there's
a high CONCENTRATION of people in the area
Money Heist Season 3, Episode 4
Due to a high CONCENTRATION of cyanide...
The Big Bang Theory Season 2, Episode 13
Halothane's CONCENTRATION, 67 percent.
Money Heist Season 3, Episode 6
...to determine at what CONCENTRATION
food starts tasting mothy.
The Big Bang Theory Season 4, Episode 6
...that, I maintain, in the right CONCENTRATION
could be weaponized.
The Big Bang Theory Season 1, Episode 17