Verloock L, Joseph W, Vermeeren G, Martens L. (2010). Procedure for assessment of general public exposure from wlan in offices and in wireless sensor network testbed. Health Phys. 98(4):628-38.

The present article proposes a measurement procedure to determine experimentally wireless local area network (WLAN) radiofrequency (RF) exposure. Recently, WLANs are becoming common technology in office buildings. Few studies have investigated exposure to WLANs using Wi-Fi technology and no study has been conducted in wireless sensor testbeds. Methods to do such measurements are necessary to test compliance with safety standards such as guidelines from the International Commission on Non Ionizing Radiation Protection (ICNIRP), Institute of Electrical and Electronics Engineers (IEEE), and the Federal Communications Commission (FCC).

Objective and Methods
The current paper develops a method to measure exposure to WLAN taking into consideration all optimal settings of the measurement equipment. A new fast procedure to perform measurements for approximately 1 minunte per orthogonal field component (and 1 minute to monitor the activity of the WLAN channels) and to obtain results that are representative for 6 and 30 minute exposures are presented. Finally, WLAN exposure is measured on-site and determined for seven WLAN networks in an office environment at 222 locations (which was possible thanks to the new and fast method). WLAN exposure is determined in an office environment in a modern four year-old office building. In this building seven different Wi-Fi networks are present. The exposure for all WLANs and the WiLab in the office environment will be assessed. The power of the active WLAN signal is measured with the SA (RMS detector and max-hold in frequency domain) and the tri-axial isotropic probe during a period of 1 minute for each vector component until the signal stabilizes. The method was validated by performing measurements of the D-Link and WiLab APs, during different time durations up to 6 minutes (ICNIRP 1998) and 30 minutes (IEEE 2005).

The results showed that the average background exposure to WLAN (WiLaboff) is 0.12 V m-1, with a 95th percentile of 0.90 V m-1. With the WiLab in operation, average exposure increases to 1.9 V m-1 with a 95th percentile of 4.7 V m-1. All values are well below the ICNIRP guidelines of 61 V m-1 in the 2.4 GHz band. 

The authors report that this is the first time to determine general public exposure in a WiLab. The results of the study showed that settings chosen for the analysis have a huge influence on the measurement results.

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