The correct answer is C (20 liters) because the 20-liter sphere apparatus is the widely accepted standard for determining dust explosion severity parameters , including Kst (deflagration index) and Pmax (maximum explosion pressure) .
According to CCPS and industry standards (such as ASTM and ISO methods), the 20-liter test chamber provides a controlled, repeatable environment for evaluating the explosibility characteristics of combustible dusts. It represents a balance between laboratory practicality and representative explosion behavior , making it suitable for routine testing.
Smaller volumes such as 5 liters (A) are generally not sufficient to accurately capture explosion dynamics and may produce less reliable results. Larger vessels such as 1 cubic meter (B) are sometimes used for more detailed or confirmatory testing, but they are not typically considered the minimum standard due to cost and complexity. Option D (50 liters) is not a recognized standard for this purpose.
CCPS emphasizes that understanding dust explosibility is essential for hazard identification, equipment design, and mitigation strategies , including explosion venting, suppression, and isolation systems. The 20-liter sphere has become the industry benchmark for generating reliable and comparable dust explosion data.
