I was looking at an advertisement for a product to block cell phone radiation earlier today. The comments posted on it were both positive, and negative. People were debating the signal levels for the front and back of the phone as well as a number of other things. Much of the discussion showed a lack of understanding of the phone, and what the shield was supposed to do.
To start with, a cell phone is a duplex radio that operates on more than one radio frequency band with a sophisticated user interface. As such, it does put out some RF (Radio Frequency) energy otherwise known as radiation. This is not as scary as it sounds, because it is non-ionizing like nuclear radiation. There are many forms of non-ionizing radiation around us all the time. Light, which we need to see, is a form of radiation. At high levels, RF radiation can be dangerous. An example would be what happens to food in your microwave oven. However the phone puts out a considerably smaller amount compared to the microwave oven.
The cell phone shield comes with a demo video to demonstrate the use of the product. It shows meter readings taken from different locations around the phone both with and without the case to prove the radiation is reduced. The video then goes on to show several happy people using the phone. The flaw with the cell phone radiation shield is that the RF signal (radiation) that the phone puts out is not incidental to the operation of the phone. The RF signal radiation is critical to the ability of the phone to connect to the cell sites. If the RF signal was truly blocked as claimed, the phone would cease to function properly. One of two possibilities could be applied to what is shown in the video. Either the case is not blocking anything, which is likely since the edge of the phone can be readily seen and with most models, the antenna is located around the edge of the phone or the range of the phone has been severely reduced by the installation of the shield which would require the phone to be in a strong signal location for the cell site for the phone to work at all. The phone itself will also defy attempts to block the signal (radiation). In areas where there is a strong signal, it turns the power down to save battery power and reduce interference to other users. In a weak signal area, or when the RF signal is blocked, the phone will increase the transmitted power to maintain contact with the cell site. So, the radiation shield will cause the phone to put out more power, drain the battery faster, and reduce the range.
Additionally they claimed to reduce ELF (Extremely Low Frequency) radiation, which would be generally caused by power line magnetic fields. The phone is run on a battery, which is DC so the phone does not produce ELF radiation. However the phone will produce a small amount of audio frequencies but not at a significant level that is capable of causing any harm to living tissue. You will get much more ELF exposure sitting next to a lamp in your house than the cell phone is capable of producing.
Other examples of products that prey on the lack of understanding of people have been stickers that are supposed to absorb the radiation, or even increase the range of the phone. With sufficient techno-babble they sound almost plausible, but they have no effect on any energy that does not come in to contact with the sticker. Even if they do absorb the energy that crosses it, they do not suck it out of the room.
There is no shortage of misinformation on the Internet.