On October 3rd, 2016 we learned about

The infrared triggers that lead toddlers to fear the flush of automated toilets

My second grader is old enough to have forgotten, but my three-year-old is still very aware of a terror waiting for him every time he leaves the house: automatically flushing toilets. For most of us, these devices basically deliver on their promise of improved hygiene in public restrooms without too much annoyance about mistimed flushes. For small kids, say around the age they’re learning to use toilets in general, these motion-sensitive commodes can feel like traps, set to trigger a child-swallowing flush without warning. Which is too bad, because these kids should really have a chance to enjoy the fact that they’re flushing their poop thanks to invisible beams of light, which seems more interesting than the faux-chromed handle at home.

Looking with invisible light

Ideally, automatic toilets (and sinks) should do a lot of good. Invisible infrared light is projected pointed out across the toilet bowl, waiting for someone to approach. When a person sits down, the light should be reflected back at a sensor near the light source, telling the toilet that it’s being used, and to be ready with a flush. Once the light stops being reflected, the assumption is that the user has stepped away, and a flush is triggered. It theoretically only uses water when necessary, but also never forgets to flush either. In addition to this efficient use of water, there are less mechanical parts to service and replace, saving money in the long run.

Invisible to infrared

In practice, things don’t always work out this well. Lime and calcium can build up on the sensor, interfering with the infrared sensor’s accuracy. For my three-year-old, there’s a bit of a calibration issue. Small kids are more likely to be perched on the front of the toilet, which is close to the sensor’s threshold for sensing if it’s in use or not. Once the kid catches the toilet’s “eye,” even a small shift forward can put them out of range, triggering an unexpected flush (and setting back potty training by weeks or months for some folks.) If distance isn’t the issue, older systems weren’t well calibrated to account for darker clothing or skin. Dark colors are more likely to absorb the infrared light beam, and so the system never triggers. For toilet users, this means a lot of hand waving or using the manual flush button, but at the sink it makes washing one’s hands very difficult. Hearing this, even my very pale second grader pointed out that this basically created a racially-discriminatory bathroom.

While the latter problem is theoretically being solved by better calibrated infrared sensors (or turning lighter palms up at inactive sinks,) nervous toddlers can find solace in toilet paper. Covering the infrared sensor before a smaller person sits allows you to control when the light gets reflected or not. Hands and post-it notes can work as well, but for those interested in making more of an investment in fighting their children’s potty anxiety, there’s a dedicated sensor-blocker called the Flush-Stopper. Since body-sensing toilets are unlikely to go away any time soon, understanding that these pieces of plumbing aren’t as arbitrary or malicious as a kid might think is probably a small first step towards relief.

Source: The truth about bathroom sensors (and why they fail so often) by Phil Edwards, Vox

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