Why must hazard controls be revalidated during scale-up?

• A. Period of scale-up requires reevaluation of controls.
• B. Process conditions change; controls may no longer be adequate.
• C. Revalidation is not necessary after scale-up.
• D. Only external audits trigger revalidation.

Answer: (B)

Hazard controls must be revalidated during scale-up because the operating conditions can change when you move from a smaller scale to a larger one, and those changes can affect how well the controls actually manage risks. When you scale up, heat transfer, mixing, mass transfer, residence time, concentrations, and even impurity profiles can shift. Those shifts can alter the likelihood and severity of hazards like exotherms, pressure buildup, or runaway reactions, so the existing controls (cooling capacity, venting, interlocks, containment, monitoring) must be reevaluated to confirm they’re still adequate under the new conditions. Revalidation helps uncover new risk scenarios specific to the larger scale and ensures the hazard management plan remains robust.

A focuses on the time period rather than the reason controls might be inadequate at a larger scale, which misses the essential point that condition changes drive adequacy. D is not correct because audits aren’t the sole trigger for revalidation; internal process changes and new scale-up risks require it. C is incorrect because revalidation is indeed necessary after scale-up.