“Chlorine” is a track about the cleansing power that music has on the narrator. Chlorine, while being a deadly chemical, is used to eliminate unwanted substances. As stated in the lyrics, the chemical is compared to a “vibe” or “beat.” While the chlorine has poisonous properties and could potentially cause harm, the narrator just can’t get enough.
A similar idea is found in an earlier song when Tyler says,
In both cases, the concept of pain, or something which would generally be unwanted is flipped on its side and used as a metaphor for that which is beneficial.
On January 22, 2019, Twenty One Pilots released an official music video for Chlorine, featuring a tiny, horned, anthropomorphic bipedal monster they call “Ned”.