Why do hospitals ban the use of cell phones?
Under certain conditions. RF interference to devices such as ventilators, patient monitors, pacemakers, neonatal infant warmers, motorized wheelchairs, and anesthesia delivery equipment has been reported and documented.

In general, the presence/absence and amount of interference is a function of power and proximity. The higher the power and closer the RF source, the greater the interference. The strength of an RF field is inversely proportional to the square of the distance from its source, which means that when distance is doubled, the field is reduced to one-quarter.

Cell phones transmit intermittently whether a call is in progress or not, so that the cell sites will recognize the phone for incoming calls. The user is totally unaware when his phone is transmitting. There is no "transmit" light on a cell phone.

Most cell phone users have no understanding of radio, radiation, and interference. They think of their device as a phone, not as a transmitter. They pay no attention to its potential for interference and in all likelihood they would not recognize RFI if it were to occur.

Cell phones are likely to get within inches of patient equipment. Visualize Uncle Fred going into a hospital room to visit Aunt Minnie with a cell phone in his pocket, leaning over to give her a peck on the cheek, and his cell phone touching the leads on her cardiac monitor.

Pacemakers
There have been rare reports that cellular phones interfere with the circuitry in pacemakers when they are held close to the pacer. According to medical professionals, if you are not pacemaker dependent, this should not be a problem for you. However, if you are pacer dependent, it could be dangerous for you to use a cellular phone. Studies have shown that cellular phones could cause your pacemaker to slow down, shut off, or even speed up your heart rate.

"Whatever kind of phone you're using, it's best to avoid carrying it around turned on in your breast pocket," says Dr. David Hayes, of the Mayo Clinic. It is also suggested that people with pacemakers hold the cell phone to the ear on the opposite side of the body from the pacemaker.

As an example, the Food and Drug Administration tested 24 implantable cardiac pacemaker models for RFI from digital cellular phones. FDA used a saline tank as a torso simulator and carefully mapped the areas of RF interaction. One-third of the pacemaker models suffered RFI, but only one was affected when the distance to the phone exceeded 3.5 inches. (That model reacted when the phone was 15 inches or closer.)

Airplanes
Cell phone use on an airplane is considered to be a crime. According to aviation officials, cell phones can interfere with aircraft navigation systems and with controls for cabin pressure and air conditioning. Law enforcement officials are working to obtain technology, which will allow them to disable wireless handsets.

Gas Stations
On a related note, mobile phone use has been banned at several gas stations across the country. Research indicates that signals are able to ignite combustible materials, the main reason why cell phone use poses a risk at any place where flammable gases are present. The danger is present even when the user is not making a call; the phones emit signals even when they are in standby mode.