When does the CAZ worst case test fail?

The reason why the correct answer is identified as appropriate relates directly to the purpose of the CAZ (Combustion Appliance Zone) worst case test, which is fundamentally about ensuring safety in the operation of combustion appliances.

When the net worst case depressurization exceeds the values specified in the CAZ depressurization limit table, it indicates that the conditions in the combustion appliance zone may lead to unsafe situations, such as the potential for backdrafting or the ingress of harmful combustion products into the living space. This violation signifies that the appliance may not be functioning safely under maximum depressurization scenarios, which is critical for ensuring that venting operates effectively and that contaminants do not circulate back into the home.

Understanding the importance of keeping the depressurization within the limits set forth ensures both the efficiency of the appliance and the safety of the residents. Exceeding these limits means there could be inadequacies in the design or operation of ventilation systems or appliances, which poses a direct risk that must be addressed.