# Radio Frequency Electromagnetic Fields Exposure Assessment in Indoor Environments: A Review
## 3 Results
### Educational Buildings
#### Exposure in Private Places
For total mobile phone downlink signals the median was 5.22 \(\mu\)W/m\({}^{2}\) (equal to 0.04 V/m in terms of electric field strength, 0.11% of the ICNIRP reference level) in rural areas, 39.18 \(\mu\)W/m\({}^{2}\) (equal to 0.12 V/m in terms of electric field strength, 0.05% of the ICNIRP reference level) in small towns, 33.49 \(\mu\)W/m\({}^{2}\) (equal to 0.11 V/m in terms of electric field strength, 0.04% of the ICNIRP reference level) in suburban areas and 51.37 \(\mu\)W/m\({}^{2}\) (equal to 0.14 V/m in terms of electric field strength, 0.05% of the ICNIRP reference level) in urban areas. The biggest differences between rural and urban areas occurred in UMTS (factor 77.5), GSM1800 (factor 32.5) and WLAN (factor 10.9). Considering the signal dominance, GSM900 was dominant in all four areas. Finally, comparing the results obtained at different floors, results showed that the highest floors are more often in line of sight to mobile phone base stations and in the main lobe of the antenna resulting in higher power flux densities than those measured at the lowest floors. Another study by [PERSON] and colleagues [PERSON] and colleagues [PERSON] and colleagues [PERSON] and others (2006) was aimed at characterizing the distribution of residential exposure due to antennas, to assess how exposure to RF fields varies with distance from these point sources, and to test the association of RF exposure with the level of urbanization of the area by using personal exposure meters. A total of 200 randomly selected people were enrolled. Each participant was supplied with a personal exposure meter for 24 h measurements, and kept a time-location-activity diary. Two exposure metrics for each radiofrequency were then calculated: the proportion of measurements above the detection limit (0.05 V/m), and the maximum electric field strength. Residential address was geocoded, and distance from each antenna was calculated. Results showed that the recorded field strength was often below the detection level (0.05 V/m). The maximum electric field strength was always lower than 1.5 V/m (i.e., lowest of the 5% of the ICNIRP reference level). Exposure to GSM and DCS peaked around 280 m and 1000 m from the antennas, while a downward trend was found within a 10 km range for FM. Conversely, the exposure due to UMTS and TV signals did not vary with distance. Two recent studies [PERSON] and others (2012); [PERSON] and others (2013) assessed the exposure of a child to either a WLAN and a femtocell placed in a representative room, when both the child and the source are placed in an uncertain position. In both studies, a stochastic dosimetry approach based on low rank tensor approximation was used to develop surrogate models for fast estimating the Specific Absorption Rate (SAR) in all the possible positions of the sources and the child. Results showed that, for all the possible positions of the sources and the child in the room, the exposure values were significantly below the levels indicated in the guidelines of the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines for general public exposure ([PERSON] et al., 2013), with probability of reaching SAR values higher than 1% of the ICNIRP guidelines value was lower than 0.006.