# Electromagnetic Assessment of UHF-RFID Devices in Healthcare Environment
## 2 Materials and Methods
### Specific Absorption Rate (SAR) Values from Exposure near MO-RFID Readers  
When individuals approach the source of EMF where near-field exposure conditions are recognized (i.e., in the distance from the source shorter than the wavelength of emitted EMF or even several wavelengths), their exposure has to be assessed using the parameters characterizing the effects of EMF influence in tissues. In case of radiofrequency EMF exposure, the relevant parameter is the metrics of thermal effects--time derivative of the incremental electromagnetic energy (dW) absorbed by an incremental mass (dm), recognized as SAR values expressed in watts of absorbed EMF energy per kilogram of exposed tissue, (W/kg). The SAR is assessed as averaged over the entire exposed body and also as localized SAR averaged in particular smaller parts of the exposed body (over 10 g mass of any continuous tissue--SAR10g) [12]. SAR values are assessed by the numerical modeling of the EMF interaction between the model of EMF source and heterogeneous anatomical body model, usually with the use of Finite-Difference Time-Domain (FDTD) numerical code compliant with the requirements set forth in the relevant international standard [31]. In the international guidelines and applicable laws and regulations relevant limits regarding mentioned SAR, values have been provided aimed for assessment of EMF exposure of workers and general public. As provided for in the relevant international laws and regulations, the SAR must be assessed for all the cases of the localized exposure within reactive near-field [24]. Moreover, under the Directive 2014/53/EU (RED), it is required to take all intended and reasonably foreseeable operating conditions of radio equipment use into account for the exposure assessment [32].  
The parameters of a typical MO-RFID reader used for our simulation are presented in Table 1. As regards the exposure scenarios applied for the purpose of the study, the antenna was located vertically (similarly to the position of an external antenna in a MO-RFID reader shown in Figure 2). The exposure scenarios include, as presented in Figure 6:  
* Exposure of an operator of a MO-RFID reader grasping a gun in the hand,
* Exposure of people approaching an operator of an MO-RFID reader--scanned person or bystander.  
Figure 5: Grid and measurement points in a care room of the HUC for the AS-RFID reader assessment.  
Based on the principles of the electromagnetic hazard management system, the EMF exposure of a reader operator is assessed with respect to the exposure limits set for the worker exposure (when an operator is an informed and qualified worker and the relevant prevention measures with respect to electromagnetic hazards are applied and accurately evidenced), or with respect to the general public exposure limits (when a gun is used by a person assuming to be without a regular employment contract, i.e., with no understanding of electromagnetic hazards and where prevention measures are not applied).  
Similarly, the exposure of a scanned person or a bystander is assessed in terms of the exposure limits set for the general public exposure or worker exposure (depending upon the aim of their presence nearby a activated reader and applied electromagnetic hazards management system).  
Numerical simulations were carried out with the use of anatomical numerical male model and Sim4 Life software (Zurich Med Tech, Switzerland) and Finite Difference Time-Domain solvers (FDTD). The FDTD method is a solution of Maxwell's curl equation in the time domain [31]. The uncertainty of the numerical simulations (i.a. related to the model of EMF source, dielectric properties of the model of human body and model resolution (staircase approximation)) was estimated as not exceeding \(\pm\)1 dB (K = 1), within the range compliant with the state of the art in the field [33; 34].  
An accurate description of the work is presented here, however additional information is available in [12].