To toggle Red Alert on or off, click the "!" button next to the cycle speed control. When activated, the button and screen edges will glow red and the words "Red Alert" will appear highlighted in the notification area. An audible klaxon also plays in the background.
During Red Alert, all duplicants will enter a state of emergency and ignore their essential needs (sleeping, breathing, et cetera) in order to focus solely on their assigned jobs, allowing them to be completed more quickly and efficiently. This, consequently, results in rapidly rising stress from lack of or interrupted sleep, zero toilet breaks and increasing hunger (Red Alert also causes +50% stress/cycle). In the long run, it also presents a high risk of death from starvation (because eating is ignored) and suffocation (if forced to work in a non-breathable atmosphere).
In some cases, going to Red Alert is critical to survival. For instance, if a duplicant is stranded during the night (when all other duplicants are normally asleep) and in imminent danger of dying from the elements before daybreak. In a case like this, the player may go to Red Alert and force all available colonists into excavating and constructing (at maximum priority) a path to the stranded duplicant.
It can be used to exacerbate stress on Vomitters & Ugly Criers so that they generate water/polluted water sooner.
Also, it can be used to mitigate the effects of stress responses; Vomitters will still vomit, but Ugly criers will not cry and Binge Eaters will not eat. Diseased Dupes will rarely express themselves. It can also be flashed (turn on & quickly back off) to wake up Narcoleptics. However, Destructive Duplicants will still attack equipment and people with Flatulence will still fart.