Soap dispensers use near-infrared technology, sending an invisible light from an LED bulb, which sense hands to dispense soap. The soap tends to not dispense at all, since the hand has to act as a reflector to the light.
The event that started the infrared sensor being inaccurate accusations was with an experience an African American guest had at a fantasy convention. The African American visitor was at the Dragon Con sci-fi fantasy convention and had gone to the bathroom in the host hotel with his Caucasian friend. When he hovered his hand under the soap dispenser, he expected the soap to follow. He waited and tried again. No soap was dispensed. When his Caucasian friend, Larry did the same, the soap ejected onto his hand. Why had the soap not been dispensed when the African-American man had attempted to use it when his white friend got it to work easily? Words got out and this led to the company being put under fire for its racially discriminatory machine that doesn’t work with darker skin toned people.