What safety feature prevents the chainsaw from starting if improperly handled?

The chain brake is a vital safety feature designed to enhance the safe operation of a chainsaw. It serves to prevent the chain from moving when the chainsaw is started or handled improperly, which significantly reduces the risk of accidental injuries. When engaged, the chain brake effectively stops the chain from rotating, ensuring that the operator is protected from unexpected chain movement during startup or when the chainsaw is being manipulated. This feature is crucial for both beginners and experienced operators, as it reinforces safe practices while using the machinery.

In contrast, the other options do not serve this specific function. The fuel cap is important for preventing spills and maintaining fuel integrity, while the air filter is essential for the performance and longevity of the engine. The throttle lock can help control engine speed but doesn't prevent the chainsaw from starting or running if not handled correctly. Thus, the chain brake stands out as the primary feature that ensures safe handling during ignition.