Under what condition does a spillage test fail?

A spillage test is performed to ensure that combustion appliances are venting properly and that there is no reverse flow of flue gases into the living space. The correct answer indicates that the test fails when flue gases spill for more than 60 seconds post-startup, which signifies a potentially dangerous situation.

Typically, during the operation of a combustion appliance, especially at startup, it is important for the flue gases to be properly exhausted. If spilling occurs for longer than 60 seconds, it indicates that the appliance is not drawing sufficient air to create a proper draft, which may lead to hazardous conditions such as carbon monoxide entering the home.

In contrast, turning off the appliance for maintenance can be a routine procedure and doesn't indicate an issue with venting; stable pressure in the combustion appliance zone (CAZ) generally reflects proper conditions for operation; and while ambient temperature can affect combustion, it is not a direct failure criterion for spillage testing. Thus, prolonged spillage indicates a serious failure in the combustion appliance's venting system, making it essential to address before further use.