Which category would NOT typically involve a low-heat appliance?

In the context of low-heat appliances, it is important to understand the operational characteristics and applications of different devices listed. Low-heat appliances are generally designed to operate at lower temperatures and are typically used for specific heating functions.

Commercial steam boilers are designed for high-temperature operation and are used in various scenarios that require steam generation for heating, industrial processes, or other applications. These boilers operate at temperatures and pressures that significantly exceed the typical low-heat range, making them unsuitable for classification as low-heat appliances.

On the other hand, water heaters, residential gas fireplaces, and furnaces are generally designed for lower temperature applications. Water heaters are meant to heat water for domestic use, typically at lower temperatures. Residential gas fireplaces are used for ambiance and may operate at low heat settings. Furnaces can vary in their heating capacity but often include low-heat options for residential heating, especially in localized heating requirements.

Thus, the distinction lies in the operational characteristics and intended use of the appliances, with commercial steam boilers firmly placed outside the category of low-heat appliances due to their high-temperature nature.