What is the lower bound of Class B extinguisher ratings?

• A. 1-B
• B. 2-B
• C. 5-B
• D. 10-B

Answer: (A)

The concept being tested is how Class B extinguisher ratings are structured and what “lower bound” means in that scale. For Class B (flammable liquids), the rating uses a number followed by B to indicate the approximate area, in square feet, the extinguisher is rated to cover. A larger number means the extinguisher can handle a larger fire; a smaller number means less capacity. So the lower bound is simply the smallest rating that exists on the Class B scale. Among the options, the smallest rating is the one representing the least capability, while the others show progressively larger capacities.