If a fire has vented out one or two windows, how long has it typically been at flashover?

When a fire has vented out of one or two windows, it usually indicates that the fire has reached a significant level of development. At this stage, it is likely within the timeframe of 1 to 5 minutes post-ignition that flashover has occurred. Flashover is a rapid transition from a fire's growth phase to a fully developed stage, characterized by extreme heat and the simultaneous ignition of all combustible materials in the room.

The progression of a fire follows a fairly predictable pattern, where the initial growth phase can lead to flashover if sufficient fuel and heated gases are present in the confined space. The presence of flames visible through one or two windows suggests that the fire has gained enough intensity and heat, reaching a temperature close to 1100 degrees Fahrenheit (593 degrees Celsius), which is typical for flashover to occur within this timeframe.

Therefore, identifying the 1 to 5 minutes period as the critical time frame for flashover aligns with fire behavior patterns studied within the field, emphasizing the importance of rapid assessment and response during fire situations for saving lives and minimizing damage.