This line comes from Half-Life, the 1998 first-person shooter by Valve, and is spoken by the player's HEV suit, the armored Hazardous Environment suit worn by Gordon Freeman. The suit narrates the player's condition in a calm robotic female voice, announcing fractures, restored power and environmental hazards, and the biohazard warning became one of its most quoted alerts. Decades later it circulates on soundboards as a shorthand for contamination, infection or filth, because a machine calmly declaring a disaster sounds funny over footage of a messy bedroom or a questionable leftover.