When a device box contains a duplex receptacle, a ____ volume allowance is to be counted for the device.

In the context of electrical boxes and their volume allowances, when a device box contains a duplex receptacle, a double volume allowance is applied. This is because a duplex receptacle essentially counts as two receptacles when calculating the box size needed to accommodate the device safely and efficiently.

The National Electrical Code (NEC) stipulates that for each receptacle outlet, specific volume allowances must be made for the box to ensure that there is enough space for safe wiring and to prevent overheating. Thus, when a duplex receptacle is present, the volume requirement effectively doubles compared to a single receptacle, hence the term "double" applies. This consideration is crucial for compliance with electrical codes, ensuring safety and proper installation in any electrical work.

Other types of receptacles or configurations may have their specific volume requirements, but in the case of a duplex receptacle, the use of a double volume allowance aligns with both industry practice and code requirements.