## 4 Discussion
Higher concentration of pollutant and shorter distance to the source, reduce the response time and consequently increased the recovery time. As a result, the visualized saturation state of Figure 10 exhibits the concentrations beyond the boundary of the prototype. The results of skin temperature as a physiological parameter are influenced by external players. Environmental parameters (e.g., air temperature) and the mode and location of wearability affect the measured output. Comparing the recorded skin temperature with the written protocol during the tests, \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Device** & **Domain** & **Location** & **Data** & **Data** & **Description** \\  & & & **Transmission** & **Processing** & **Protection** & **(Storage)** & \\ \hline
**VCSEL [48]** & physiological & ear-wom & BLE & centralized & no & It is a sign-parameter, low-cost, and long-term pulse-ovimeter monitoring, developed for COPD patients. \\
[2] & physiological, environmental & attach to garment and helmet & BLE, LoRa & distributed & no & It is a hybrid distributed system for health and safety monitoring. \\
**VATANN [46]** & behavioral, & garment & GSM & distributed & no & It measured ECG, skin temperature, and detect fall. \\
**SweetAge [18]** & physiological & wrist-worn & Bluetooth & distributed & no & Skin temperature, heart rate, and user activities are monitored. Moreover, commercial devices can be integrated into the system. \\
**HealthWear [47]** & physiological & arm-band & GPRS & distributed & no & ECG, pulse rate, and respiratory movement and rate are integrated into a convenient T-shirt. \\
[48] & behavioral, physiological, & head-set & BLE & distributed & no & A camera is used for motion tracking and gesture detection. \\
[29] & physiological, & wrist-worn, chest-worn & BLE, WiFi & distributed & no & Two wearables with several integrated sensors measure ECG, pitch angle oxygen, skin impedance, and strain VOCs and O\({}_{5}\), temperature, and humidity. \\
**CHRONIOUS [49]** & environmental, behavioral, & garment & BLE & distributed & no & The approach is using several wearables integrated into a T-shirt for data collection. Besides, external devices are used for supporting additional physiological parameters and integrated into the system. \\
[50] & physiological, environmental & & BLE, Bluetooth & distributed & yes & It is a physiological-environmental- behavioural parameters monitoring with a flexible IoT gateway to adopt different commercial devices. \\
**WELCOME [50]** & behavioral, & light-vest & WiFi & distributed & no & WELCOME supports a comprehensive physiological monitoring through Body Area Network. It also supports decision support system. \\
**Our prototype** & environmental, wrist-worn & BLE & centralized & yes & Our device supports sensor activation/deactivation. It is low-power and prolonged monitoring. \\  & behavioral & physiological & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison of the proposed device with the most applicable works in COPD patient’s and safety monitoring. indicates the effect of air temperature on the output. Swinging the data under the constant environmental conditions can be due to movement of the prototype caused by a loose attachment. However, there are limitations of the device. The boundary measurement of CO, NO\({}_{2}\), UV index, and loudness are 0 to 1680 ppm, 0 to 52.8 ppm, 0 to 9, and 32 to 85 dB, respectively. The resolution is 5 ppm, 0.1 ppm, 1, and 1 dB, respectively. It is also worth mention that the multi-gas monitoring works only in BLE-paired status. In contrast to existing approaches (Table 9), our device supports internal data storage in BLE-disconnected mode for approximately 10 h. So far, we recommend the immediate data transmission of the logged data when BLE is resumed, which will be performed automatically in future versions of the device software.