Prime universe
(Capcom's primary storyline)

P-ε (P-Epsilon) or known by its development code UMB No.21 is an Umbrella-created toxic gas. It was designed to stop out-of-control B.O.W.s who have broken out. However, when in contact with Plant 43, it causes them to mutate into a more dangerous form, where they create a poison ability. The stated explanation is that some species are able to extract toxins from the gas and use these toxins against threats.[1]

Resident Evil 2 remake

In the 2019 remake of Resident Evil 2P-ε is specifically an herbicide.  It must be synthesized and deployed to damage Plant 43 to open up an area of the greenhouse .  Synthesis involves cooling the subtance to cryogenic temperatures.[2]

Further notes

Earlier in the franchise development, P-ε was an anti-"t" gas, as it was Lore at the time that only certain enemies were infected with the virus. The Ivies, not infected with "Epsilon", are thus not destroyed by the gas.


  1. Resident Evil 2 (1998), file: "P-Epsilon Gas Report".
  2. Resident Evil 2 remake (2019), file: "Herbicide Synthesis".
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