What condition warrants the use of the hand or emergency brake during CNG transfer?

The use of the hand or emergency brake during the transfer of compressed natural gas (CNG) is critical for safety reasons. When conducting this process, the vehicle must remain stationary to prevent any accidental movement that could lead to hazardous situations, such as gas leaks or accidents. Engaging the hand or emergency brake ensures that the vehicle is secure during the transfer of CNG, allowing the driver to focus on the operation without the distraction or risk of the vehicle rolling or shifting unexpectedly.

In contrast, while unloading cargo or parking a vehicle may involve employing the brake, these actions do not inherently carry the same specific safety risks associated with the CNG transfer process. Similarly, while entering the dispensing area requires caution and potentially the application of the brake, the explicit need for the hand or emergency brake is most pronounced during the actual transfer of CNG, where the stakes are particularly high due to the flammable nature of the material being handled.