The Universe of Discourse

Mon, 24 Jan 2022

Excessive precision in crib slat spacing?

A couple of years back I wrote:

You sometimes read news articles that say that some object is 98.42 feet tall, and it is clear what happened was that the object was originally reported to be 30 meters tall …

As an expectant parent, I was warned that if crib slats are too far apart, the baby can get its head wedged in between them and die. How far is too far apart? According to everyone, 2⅜ inches is the maximum safe distance. Having been told this repeatedly, I asked in one training class if 2⅜ inches was really the maximum safe distance; had 2½ inches been determined to be unsafe? I was assured that 2⅜ inches was the maximum. And there's the opposite question: why not just say 2¼ inches, which is presumably safe and easier to measure accurately?

But sometime later I guessed what had happened: someone had determined that 6 cm was a safe separation, and 6cm is 2.362 inches. 2⅜ inches exceeds this by only !!\frac1{80}!! inch, about half a percent. 7cm would have been 2¾ in, and that probably is too big or they would have said so.

The 2⅜, I have learned, is actually codified in U.S. consumer product safety law. (Formerly it was at 16 CFR 1508; it has since moved and I don't know where it is now.) And looking at that document I see that it actually says:

The distance between components (such as slats, spindles, crib rods, and corner posts) shall not be greater than 6 centimeters (2⅜ inches) at any point.

Uh huh. Nailed it.

I still don't know where they got the 6cm from. I guess there is someone at the Commerce Department whose job is jamming babies’ heads between crib bars.

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