Blackout

A Blackout is an event that causes all the lights inside the building to go out. It is triggered manually by breaking the powerbox as an Infected (or by having the trolchete) behind the big generator in the Engine Room.

Once the powerbox has been broken, all the lights will be red for a split second and you will hear a ringing sound before they go out.

During a blackout, all Infected will have glowing eyes with the colors based on the animal they are, excluding the Dark Latex, as they already have glowing eyes to begin with.

During a blackout
The Phone is the only reliable light source for the humans as not having one means navigation is extremely hard, stuff spawned from lockers can act as a light source if not picked up, or shooting infected with an Alarm Gun, though make sure they keep moving or else the light may go off and you will be stuck in darkness again.

As for Infected, they are able to see without problem due to having night vision, though when the blackout ends, they will be temporarily blinded.

The only two areas that have a considerable amount of light during a blackout are the Pool and Crystal Cave.

A blackout lasts 5 minutes (300 seconds). After a blackout ends, the powerbox is invulnerable to damage from infected for 25 minutes, then the powerbox can be damaged again. The powerbox can also slowly regain health as it is not attacked.

Trivia

 * If you are wearing a Roblox cosmetic that covers your whole face and eyes, other players will not be able to see the glow of your eyes, allowing you to be a bit more stealthy during a blackout.
 * If you join a server after a blackout has occurred, the powerbox will have a nametag and health bar, shown in the last image below. It appears that the powerbox is an NPC that you can damage, hence why it can regain health.