## 5 Conclusions  
The results of this work show that the absorption in the user's head of an EMF emitted by a wearable IoT device using a MIFA, for example applied to alert workers against hazards in the work environment, may have a significant influence on humans when used directly on the head [44]. Locating the MIFA on a helmet may sufficiently reduce the level of the IoT device user's exposure to EMF. Based only on the presented results, it is impossible to indicate the best (safe in terms of lowest SAR values) exposure scenario. This requires further research, taking into account more detailed exposure scenarios such as anatomically-based models of the human body, other locations for wearable devices on the worker (e.g., on wrist, chest, arm, leg, etc.), various antenna plane locations against the body surface (parallel or normal) and device ground-plane normal or parallel to the skin, rather than investigating more sophisticated models of wearable IoT devices.  
These studies indicate that locating the wearable device at a very short distance (a few millimetres) from the human body causes a high mismatch with the desired operating frequency and the antenna's performance. This may result in the need to increase the input power to the device antenna to ensure a stable radio-link between the device and other WSN components, the access point or the main unit. A consequence of this is also an increase in the SAR value. Hence, a good and safe wearable IoT device is one that has been designed and optimised for the dedicated use of the device (with low power needed to set a stable radio-link receiver-transmitter), for example in a headband or as a watch. For this reason, research on new technical solutions (new antenna designs, new materials and designs of IoT devices) is recommended to improve the parameters of radio links created with the use of the IoT device (by means of its operation at low EMF emission, which also means automatically reducing the SAR value in the user's body).  
Conceptualization, P.Z., J.K., K.G. ([PERSON]), L.M., R.M. and V.R.; methodology, P.Z., K.G. ([PERSON]) and K.G. ([PERSON]); validation, P.Z. and K.G. ([PERSON]); formal analysis, P.Z., J.K. and L.M.; investigation, P.Z., J.K., K.G. ([PERSON]), V.R., L.M., R.M., K.G. ([PERSON]) and A.S.; resources, K.G. ([PERSON]), L.M. and A.S.; data curation, P.Z. and K.G. ([PERSON]); writing--original draft preparation, L.M., P.Z., J.K. and V.R.; writing--review and editing, L.M., P.Z. and J.K.; visualization, P.Z. and R.M.; supervision, J.K.; project administration, P.Z., L.M., R.M. and V.R. All authors have read and agreed to the published version of the manuscript.  
Results of research tasks (II.PB.15, 2.G.04, 2.G.05) carried out within the National Programme \"Improvement of safety and working conditions\" partly supported in Poland in 2017-2022--within the scope of research and development--by the Ministry of Science and Higher Education/National Centre for Research and Development and --within the scope of state services--by the Ministry of Family, Labour and Social Policy (CIOP-PIB is the Programme's main co-ordinator) and the project \"Electromagnetic Characterisation in Smart Environments of Healthcare and their involvement in Personnel. Occupational and Environmental Health\" (PI14 CIII/00056) funding from the Sub-Directorate-General for Research Assessment and Promotion in Spain (Instituto de Salud Carlos III) and as part of the research activity of the Warsaw University of Technology.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.