A highly combustible compound present in the atmosphere of Paraagan II, whose ignition killed some 3,600 colonists and was at first blamed on a shuttlepod from Enterprise NX-01 in Shockwave.
Tetrazine is a volatile compound released by the mining operations of the Paraagan II colony, where it gathers in a layer of the upper atmosphere. Ships visiting the colony are required to follow strict protocols and close their plasma ducts so that engine exhaust cannot set it alight.
In the Enterprise episode Shockwave in 2152, a shuttlepod carrying Archer, T'Pol and Reed descends towards the colony and the tetrazine ignites, burning off the atmosphere and killing all 3,600 inhabitants. Although Reed is certain the vents were sealed, the disaster appears to be Starfleet's fault and the mission of Enterprise is cancelled.
The temporal agent Daniels then tells Archer the truth: a cloaked Suliban vessel fired a plasma stream to ignite the gas and discredit Earth. Evidence recovered from a Suliban ship clears the crew, and the incident becomes a turning point in the Temporal Cold War.