How to complete Marathon Tox Clear events

The Marathon Tox Clear event is an optional challenge that lets you either brave a room of toxic gas to grab its loot or find a way to deactivate the gas. The gas is highly dangerous, and the Hazard Override key needed to clear it is quite rare, so many runs won’t make it worth the risk without preparation.

To vent the gas you need a Hazard Override Card, a type of Enhanced Key found while looting. These cards are uncommon but can turn up in containers or on dead players; you can exfil with one and store it in your vault to use on a later run. With a key in hand, look for a red laptop near the Tox Clear room whose screen shows the same symbol as the inactive gas-extraction devices inside.

Using the key on that laptop clears the gas briefly—about 30 seconds—so you must move fast to loot the trunks before the room refills. You can open the door and loot without venting, but you’ll suffer the Toxin damage-over-time and mechanical debuffs that weaken healing—effects that can even kill you.

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