Poka-Yoke and Childproofing.

A major concern in any household with toddlers is safety. The little tykes just get into everything, especially if it’s dangerous or off-limits. As a result, making your home safe for children (despite their best efforts) could not be more important.

We’ve learned one simple lesson while childproofing our house:

Active safety measures are not enough. You MUST have passive safety measures as well.

The difference between active and passive measures is simple: Does the safety measure rely on your constant attention and participation to be effective? If so, it’s active. If not, it’s passive.

The reason why this distinction is important: It’s not enough to just “try really hard to keep an eye on the kids.” Sooner or later, you will be distracted or careless, just for a moment, and when that happens, all bets are off. To keep your kids safe, you have no choice but to have a backup method that doesn’t rely on your active attention.

For instance, until your kids are old enough to handle stairs without supervision, you really need to have baby gates. Your careful attention will eventually fail, if just for a second, and that’s more than enough time for a nasty tumble to take place. The metal of the safety gate, on the other hand, is passively solid and unyielding every moment of every day whether you are paying attention or not.

The idea that active safety measures must be backed up by more passive measures is common outside of child care as well. Most people acknowledge that even if you drive very carefully, wearing seatbelts and having a car with airbags are still pretty good ideas. And every carpenter knows that whatever your experience level, protective goggles are a great investment.


In lean production, these passive safety or defect-prevention methods are referred to by the term “poka-yoke.” Some observers translate poka-yoke as “idiot-proofing,” which seems unnecessarily pejorative. I prefer the alternate translation, “mistake-proofing.” Poka-yoke wants to make it impossible for people to make mistakes, whether through inattention, poor training, fatigue, or any other reason.

Industrial examples of poka-yoke are generally simple yet surprisingly effective physical “hacks.” Taping a piece of cardboard over a machine input can make it impossible to put a piece of raw material in the wrong way. Installing a “dead man’s switch” on a device can make it impossible for the operator to stick a vulnerable hand into a dangerous spinning mechanism while the machine is running (because the opening and the switch keeping the machine on are too far apart for the operator to simultaneously reach both). Using a simple torque-limiter on a screwdriver can make it impossible to overtighten screws. And so on. When a mistake becomes impossible, poka-yoke is happening.

Baby gates, outlet covers, doorknob spinners and cabinet locks are all poka-yoke measures that eliminate the kinds of household mistakes that can hurt a child. I’m going to start looking around my home for more ways to reduce mistakes by making them otherwise impossible to perform. Here’s a few I just thought up:

  • Make all of your outside door locks deadbolts that require a key to engage the lock. If you have to have a key on you to lock the door, it’s impossible to lock yourself out just because you left your keys inside.
  • Block your door with your briefcase to make sure you won’t forget it in the morning. It’s impossible to overlook something you have to move to get out of the house.
  • Take advantage of a built-in poka-yoke system and make sure your house outlets are polarized, making it impossible to put in a polarized plug the wrong way.

Next time I’ll talk about how a poorly-designed poka-yoke device in our home actually manages to make the situation worse rather than better.


About adbenking

A journeyman sociologist living in Chicagoland.
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One Response to Poka-Yoke and Childproofing.

  1. Pingback: Bad poka-yoke is worse than none | Everyday Lean

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