A number of conditions may limit the effectiveness of an alarm or warning. These should be taken into account when planning or evaluating an alarm system. In general, a multi-modal is less likely to be missed.
Parameter |
Interfering Condition |
color |
color blindness |
text |
visual impairment |
flash frequency |
can be missed during a passing glance if frequency is too slow |
symbol |
not understood or illegible |
language |
not understood or illegible |
technical language |
not understood |
sound |
deafness, earphones or earplugs |
vibration |
peripheral neuropathy |
light emitting or required for reading |
light or power out |
sound emitting |
defective sound generator |
electricity required |
power outage |
meaning |
cognitive or intellectual impairment |
A simple outage of an alarm or warning system can have devastating consequences. A simple light bulb could have saved the Andrea Doria.