5
3.If unintended movement or brake release occurs, turn the powered wheelchair off as
soon as it is safe.
4.Be aware that adding accessories or components, or modifying the powered wheel-
chair, may make it more susceptible to interference from radio wave sources.(Note:
It is difficult to evaluate the effect on the overall immunity of the powered wheel-
chair).
5.Report all incidents of unintended movement or brake release to the powered
wheelchair manufacturer, and note whether there is a radio wave source nearby.
Power wheelchairs and motorized scooters (in this section, both will be referred to
as powered wheelchairs) may as susceptible to electromagnetic interference (EMI),
which is interfering electromagnetic energy emitted from sources such as radio
stations, TV stations, amateur radio (HAN) transmitter, 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 inten-
sity of the EM energy can be measured in volts per meter(V/m).Each powered
wheelchair can resist EMI up to a certain intensity. This is called “immunity level”.
The higher the immunity level, the greater the protec
t
ion. At this time, current
technology is capable of providing at least 20 V/m of immunity level, which would
provide useful protection against common sources of radiated EMI.
Following the warnings listed below should reduce the chance of unintended brake
release or powered wheelchair movement that could result in serious injury:
Do not turn on hand-held personal communication devices such as citizens band (CB)
radios and cellular phones while the powered wheelchair is turned on.
TURN OFF YOUR POWERED WHEELCHAIR AS SOON AS POSSIBLE WHEN
EXPERIENCING THE FOLLOWING:
‧
Unintentional motions
‧
Unintended or uncontrollable direction.
‧
Unexpected brake release
The FDA has written to the manufacturers of power wheelchairs asking
them to test new products to be sure they provide a reasonable degree of
immunity against EMI. The FDA requires that a powered wheelchair
should have an immunity level at least 20 V/m, which provides a reason-
able degree of protection against more common sources of EMI. The
higher the immunity level, the greater the protection. Your powered
wheelchair has an immunity level of 20 V/m which should protect against
common sources of EMI.
