Works well, reacts on everything. Measurements increase close to different electronic devices. In the middle of the room shows zero. That's for electric field, measured in V/m. Sound and red flash alarm is fixed at 40 V/m, so instantly flashes because each device and powered wire (even walls) in house gives more than that. As for magnetic field, measured in microteslas, it reacts only on working electric motors, otherwise zero in home environment. I bought this thing only because I live very close to high power lines. So directly under powerlines around 3 meters above the ground I found about 600 V/m and some magnetic field, don't remember what was the number now. But near the wall of my house is almost zero and I'm happy about that. However I really don't know how exact are measurements with this device. You should be aware that this device is not for measuring high frequency radiation coming from mobile phones, wi-fi routers etc.
E-field not working properly.