# Radio Frequency Electromagnetic Fields Exposure Assessment in Indoor Environments: A Review
## 3 Results
### Educational Buildings
#### 3.4.4 Comparison between Different Types of Indoor Environments
The average and maximal total electric-field values in schools, homes, generic public places and offices, were equal to 0.2 and 3.2 V/m in schools (0.7% and 11.4% of the lowest ICNIRP reference level for the considered frequency band), 0.1 and 1.1 V/m in homes (0.36% and 3.9% of the lowest ICNIRP reference level for the considered frequency band), and 0.6 and 2.4 V/m in public places (2.1% and 8.6% of the lowest ICNIRP reference level for the considered frequency band), and 0.9 and 3.3 V/m in offices (3.2% and 11.8% of the lowest ICNIRP reference level for the considered frequency band). In the considered schools, the highest maximal and average field values were due to internal RF-EMF sources (WiFi), while in the considered homes, public places, and offices, the highest maximal and average field values originated from telecommunication signals. The lowest exposure levels were observed in homes. Internal sources, such as the WiFi, contributed on average more indoors (31.2%) than outdoors (2.3%), while the average contributions of external sources (broadcast and telecommunication sources) were higher outdoors (97.7%) than at indoor positions (68.8%). In indoor measurements, FM, GSM, and WiFi dominate the total exposure. The average contribution of the emerging technology LTE was only 0.6%. In a study by [PERSON] et al. [74], 15-min spot measurements in 263 rooms in 101 primary schools and 30 private homes in Amsterdam, the Netherlands were assessed. The authors found an overall power density with mean value equal to 0.041 mW/m\({}^{2}\) (0.12 V/m in terms of electric field strength, equal to 0.44% of the ICNIRP reference level), with the GSM900, GSM 1800 and UMTS contributing to exposure levels equal to 0.02, 0.012 and 0.01 mW/m\({}^{2}\), (0.09, 0.07 and 0.06 V/m in terms of electric field strength, equal to 0.23%, 0.12% and 0.09% of the ICNIRP reference levels for each frequency band) respectively. The authors did not report the separate exposure levels for schools and homes. Another study [6] was based on temporal 24-h measurements of all the RF signals, including LTE, present in home and schools. Measurements were performed with spectral narrowband equipment. The maximal levels of exposure in the different frequency bands were found to be equal to 0.16 V/m (0.6% of the ICNIRP reference level) for broadcasting, 1.13 V/m for telecommunication (about 3% of the ICNIRP reference level), 3.10 V/m for DECT(about 3% of the ICNIRP reference level) and 1.70 V/m WiFi 2.4 GHz (about 2.8% of the ICNIRP reference level) in schools, and to 0.23 V/m for broadcasting (about 0.8% of the ICNIRP reference level), 0.12 V/m for telecommunications (about 0.32% of the ICNIRP reference level), 0.16 V/m for DECT (about 0.42% of the ICNIRP reference level) and 0.68 V/m for WiFi 2.4 GHz in homes (about 1% of the ICNIRP reference level). The largest maximal variations, defined as the ratio of the maximal momentary electric-field value to the minimum electric-field value over the considered time interval, were obtained for the cordless telephony (DECT) signals (10.6 dB) and for the WiFi 2.4 GHz signals (12.7 dB). Temporal variations of broadcasting signals and telecommunication signals were much lower. Thus, indoor sources exhibit the largest variations indoor and are the most critical for practical exposure assessment and comparison with existing guidelines. A further comparison between the indoor exposure in different microenvironments can be found in a study by [PERSON] et al. [2]. Personal RF-EMF exposure was measured in 529 children (ages 8-18 years) in Denmark, the Netherlands, Slovenia, Switzerland, and Spain by using personal portable exposure meters for a period of up to three days between 2014 and 2016 and repeated in a subsample of 28 children one year later.