Combustion Appliances Safety Test (CAST) Practice Test

The calculation of Net worst case depressurization involves determining the difference between the gross depressurization and the base depressurization. By subtracting the base depressurization from the gross depressurization, you account for the natural or normal building pressures and conditions, allowing you to find the worst-case scenario under adverse conditions. This method is crucial in understanding how negative pressure could potentially affect appliance operation and safety, particularly in combustion appliances. This approach ensures that any factors contributing to increased depressurization are accurately represented, thereby aiding in safety assessments and compliance with relevant regulations. This makes the choice of gross minus base the correct method for calculating net worst case depressurization.