## 1 Introduction
### Aims and Contributions of the Presented Research Work
The collected data are acquired and processed by a suitably designed electronic board based on the SAMD21G18A microcontroller. This section also includes a Bluetooth Low Energy (BLE) module for forwarding the acquired data to a cloud platform using a mobile IoT gateway installed on the user's smartphone. The device is meant to monitor the physical and environmental conditions of workers who operate in particularly harsh workplaces (food, chemical, steel industries, etc. ), reducing the risks of accidents or mitigating their consequences. The developed wearable device represents the source nodes of a monitoring system based on a cloud platform (IBM Cloud), which displays, processes, and stores the gathered data. The developed system enables remote monitoring of workers' parameters and sends alarm notifications to users and companies' security managers if abnormal parameters are detected. Furthermore, a mobile application was developed to gather data from wearable devices and forward the acquired data to the cloud platform through Message Queue Telemetry Transmission (MQTT), acting as a mobile IoT gateway. In addition, the developed device integrates a multisource energy harvesting section to scavenge energy from sources associated with the human body. Specifically, the smart garment deploys thin-film photovoltaic panels, thermoelectric generators (TEGs), and flexible piezoelectric transducers, allowing the harvesting of light energy, body heat, and mechanical energy related to joint movements. The extracted energy is accumulated in a 380 mAh lithium polymer (LiPo) battery to feed the integrated sensing section. Field tests demonstrated that the harvesting section could guarantee the energy autonomy of the developed wearable device in real operating conditions. The main contributions of the presented scientific work are:  
* Development of a low-power and versatile wearable solution for monitoring the operating conditions of workers who operate in particularly harsh environments. The aim is to create a monitoring system fully based on the edge computing paradigm, \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Gas Species** & & **Exposure Limit** & **Advisory Body** \\ \hline \multirow{2}{*}{Carbon Monoxide (CO)} & - & 23 mg/m3 (10 ppm) according to TWA standard & WHO 1 \\  & - & 117 mg/m3(100 ppm) according to the STEL standard & \\ \hline \multirow{2}{*}{Hydrogen sulfide (H2S)} & - & 7 mg/m3 (5 ppm) according to the TWA standard & \multirow{2}{*}{SCOEL 2} \\  & - & 14 mg/m3 (10 ppm) according to STEL standard & \\ \hline \multirow{2}{*}{Formaldehyde (CH2O)} & - & 0.246 mg/m3 (0.2 ppm) according to TWA standard & \multirow{2}{*}{SCOEL 2} \\  & - & 0.490 mg/m3 (0.4 ppm) according to the STEL standard & \\ \hline \multirow{4}{*}{Oxygen (O2)} & - & 15–10\%: labored breathing, fast pulse, and difficulty in motor coordination; & \\  & - & 12–10\%: vertigo and cognitive difficulties; & \\ \cline{1-1}  & - & 10–8\%: nausea, vomiting, semi-unconsciousness, ashen face, fainting, and & \\ \cline{1-1}  & & brain damage & \\ \hline \hline \end{tabular}  
* World Health Organization (WHO); 2 Scientific Committee on Occupational Exposure Limits (SCOEL).  
\end{table} 
Table 1: Table summarizing the limit values of the detected gas species. allowing remote control of working conditions to detect the lack of a healthy state in the workplace and accidents suffered by workers. * An efficient and conformable multisource energy harvesting section integrated into the garment, tailored to scavenge energy even in conditions with low illuminance and a small difference in temperature between the skin and environment. * Low-power conditioning sections for electrochemical gas sensors, integrated into the garment to detect the environmental concentrations of dangerous gas species. * A custom gateway mobile application to gather data from the wearable device and forward them to a cloud application, where they are displayed, stored, and processed to detect dangerous situations for workers.