The 20-minute rule applies to which types of construction?

The 20-minute rule is a guideline in firefighting that helps determine the amount of time before flashover occurs in buildings of specific construction types, primarily focusing on the behavior of fire in relation to building materials and design. It is particularly relevant to Type III and Type V constructions.

Type III construction, often referred to as "ordinary" construction, has exterior walls made of non-combustible material, but the interior structural elements are typically made of combustible materials such as wood. This combination can lead to rapid fire spread once the interior is ignited. Similarly, Type V construction is characterized by light-frame wooden construction, where both the exterior and interior elements are primarily combustible. Fire can spread quickly in these types of structures, therefore, the 20-minute rule assists firefighters in predicting critical intervals for intervention and fire control.

Understanding the 20-minute rule is essential for firefighting strategy as it indicates the timeframe for effective response before conditions may become dangerous, especially in Type III and Type V constructions. Utilizing this rule can help inform the decision-making process regarding resource allocation, fire attack strategies, and evacuation procedures.