Steel weakens around ____ degrees F and elongates ____ inch for every foot of length.

• A. 500 degrees F and 0.5 inch
• B. 1,000 degrees F and 1 inch
• C. 2,000 degrees F and 2 inches
• D. 750 degrees F and 0.75 inch

Answer: (B)

Steel loses significant strength and begins to deform noticeably as it heats in a fire. In fire service training, a practical guideline is that structural steel weakens around one thousand degrees Fahrenheit, and under those conditions it can elongate about one inch for every foot of length. That means a member one foot long could extend roughly one inch, and longer members would show proportional deformation, which helps explain why floors and beams can sag or push apart at high temperatures.

The other options underestimate or overstate the typical threshold and deformation. At around five hundred or seven hundred degrees, the weakening isn’t as pronounced, and two thousand degrees would imply far greater distortion than the common rule suggests. Keeping the one thousand degrees and one inch per foot relationship in mind helps anticipate potential failure and plan safer firefighting actions.