There are some concerns about electromagnetic interference to powered wheelchairs and scooters. You need to know what EMI (Electromagnetic Interference) is and how to prevent such incidents. The following paragraphs suggested by the Food and Drug Administration (FDA) are intended to provide you some important information about this.
Electromagnetic Interference (EMI) From Radio Wave Sources
Powered wheelchairs and motorized scooters (in this text, both will be referred to as powered wheelchairs) may be susceptible to electromagnetic interference (EMI), which is interfering electromagnetic energy (EM) emitted from sources such as radio stations, TV stations, amateur radio (HAM) transmitters, two-way radios, and cellular phones. The interference (from radio wave sources) can cause the powered wheelchair to release its brakes, move by itself, or move in unintended directions. It can also permanently damage the powered wheelchair’s control system. The intensity of the interfering EM energy can be measured in volts per meter (v/m). Each powered wheelchair can resist EMI up to certain intensity. This is called its “immunity lever.” The higher the immunity level, the greater the protection. At this time, current technology is capable of achieving at least a 20-v/m immunity level, which would provide useful protection from the more common sources of radiated EMI. The immunity level of this powered scooter as shipped, with no further modification, is not known.
There are ample sources of relatively intense electromagnetic fields in everyday environment. Some of these sources are obvious and easy to avoid. Others are not apparent and exposure is unavoidable. However, by following the warnings listed below, your risk to EMI will be minimized.
The sources of radiated EMI can be broadly classified into three types:
1. Handheld portable transceivers
Examples include: citizens band (CB) radios, “walker talkie,” security, fire, and police transceivers, cellular telephones, and other personal communication devices. Note: Some cellular telephones and similar devices transmit signals while they are on, even when not being used.
2. Medium range mobile transceivers
Examples include: those used in police cars, fire trucks, ambulances, and taxis. These usually have the antenna mounted on the outside of the vehicle.
3. Long-range transmitters and transceivers
Examples include: commercial broadcast transmitters (radio and TV broadcast antenna towers) and amateur (HAM) radios.
Note: Other types of hand-held devices, such as cordless phones, laptop computers, AM/FM radios, TV sets, CD players, cassette players, and small appliances, such as electric shavers and hair dryers, are not likely to cause EMI problems to your powered wheelchair.
Powered Scooter Electromagnetic Interference (EMI)
Because EM energy rapidly becomes more intense as one moves closer to the transmitting antenna (source), the EM fields from Hand-held radio wave sources (transceivers) are of special concern. It is possible to unintentionally bring high levels of EM energy very close to the powered scooter’s control system while using these devices. This can affect powered scooter movement and braking. Therefore, the warnings listed below are recommended to prevent possible interference with the control system of the powered scooter.
- Do not operate hand-held transceivers (transmitters-receivers), such as citizens band (CB) radios, or turn ON personal communication devices, such as cellular phones, while the powered scooter is turned ON.
- Be aware of nearby transmitters, such as radio or TV stations, and try to avoid coming close to them;
- If unintended movement or brake release occurs, turn the powered scooter OFF as soon as it is safe.
- Be aware that adding accessories or components, or modifying the powered scooter, may make it more susceptible to EMI (Note: There is no easy way to evaluate their effect on the overall immunity of the powered scooter.
- Report all incidents of unintended movement or brake release to the powered scooter manufacturer, and note whether there is a source of EMI nearby.
If unintended motion or brake release occurs, turn the power OFF as soon as it is safe.
FDA recommends that you report all incidents of unintended motion or brake release to us or your dealer, and if possible, note whether there was a radio wave source nearby at the time of the incident. You may also report to FDA’s Med Watch problem reporting program. Call 1-800-FDA-1088 and ask for Form 3500.
