Final answer:
It is true that some humidifiers have their own water heating devices, specifically those known as warm mist humidifiers or steam vaporizers, which heat the water to create steam.
Step-by-step explanation:
The statement that some humidifiers have their own water heating devices is true. There are two main types of humidifiers: cold mist and warm mist. Cold mist humidifiers, such as cold vaporizers mentioned in Figure 20.38, evaporate water into the air with little temperature increase, and they do this by passing electrical current through the water. On the other hand, warm mist humidifiers (also known as steam vaporizers) heat up the water to produce steam, which is then cooled slightly before leaving the unit as warm mist.
While cold vaporizers do not typically have heating elements since they operate using a different method to vaporize water, some other types of humidifiers indeed contain water heating devices to create warm mist. Sanitization protocols, as in sterilization with moist heat, rely on high temperatures to eliminate microbes effectively. Devices like hair dryers carry safety messages to prevent their use around water to avoid the risk of electric shock, which is a serious safety concern.