Industrial IoT (IIoT) devices are specifically designed for deployment in operational technology (OT) environments such as factories, power plants, and outdoor installations. These settings are often characterized by harsh conditions, including extreme temperatures, high humidity, vibration, dust, and exposure to corrosive materials. Therefore, a common and distinguishing characteristic of IIoT devices is their ruggedized construction to ensure reliability, safety, and a long operational lifespan. This contrasts with the majority of consumer IoT devices, which are built for more controlled and benign indoor environments.

B. Both IIoT and general IoT devices frequently use standardized protocols (e.g., MQTT, Wi-Fi, Bluetooth) to achieve interoperability within their respective ecosystems.

C. Transmitting small, periodic data packets is a fundamental characteristic of many types of IoT devices, including both consumer and industrial sensors.

D. Proprietary protocols are found in both consumer and industrial IoT sectors, often used by vendors to create closed ecosystems or for highly specialized applications.

---

1. Sisinni, E., Saifullah, A., Han, S., Jennehag, U., & Gidlund, M. (2018). Industrial Internet of Things: Challenges, and Research Opportunities. IEEE Transactions on Industrial Informatics, 14(11), 4723-4734. In Section II-A, "Requirements and Challenges," the paper explicitly states: "IIoT devices are often deployed in harsh environments, which may be characterized by extreme temperature, humidity, vibration, noise, and the presence of corrosive materials." (p. 4724). DOI: 10.1109/TII.2018.2852491

2. Cisco. (2020). Cisco Validated Design: Industrial IoT (IIoT) Networking and Data Management. In the chapter "Solution Design," the section "IT and OT Convergence Challenges" contrasts office-grade IT equipment with industrial-grade OT/IIoT equipment, emphasizing that industrial devices must be "hardened" or "ruggedized" to withstand the physical conditions of the factory floor, including wide temperature ranges, shock, and vibration.

3. Boyes, H., Hallaq, B., Cunningham, J., & Watson, T. (2018). The industrial internet of things (IIoT): An analysis framework. Computers in Industry, 101, 1-12. In Section 3.2, "Context," the authors highlight the environmental differences: "The context is the physical environment in which the ‘things’ are located... For example, a sensor on a North Sea oil rig will be in a very different context to one in a climate-controlled laboratory." This directly supports the idea that the operational environment dictates the physical characteristics of IIoT devices. DOI: 10.1016/j.compind.2018.04.015