Wherefore Art Thou Scoville?

I don't know if you've noticed that the heat ratings attributed to hot sauces tend to vary wildly depending on where you look.  I personally find it very frustrating, not because my mouth is finely tuned to exact Scoville levels and I disagree with the numbers, but because I'm not a Scoville detector and I find it useful to know whether a particular sauce I haven't tried is twice as hot or ten times as hot as a sauce I'm familiar with before buying.  They all say they're hot.  And above an arbitrary heat level, they just start saying things like "extra hot" or "super hot" or "insane", which is not a measure of heat at all, but rather of fitness for prosecution.

I think the issue mainly stems from the extremely weird, subjective, semi-scientific nature of the original Scoville scale.

Wilbur Scoville, whose Scoville Organoleptic Test outlasted his really excellent mustache as his enduring legacy.

Wilbur Scoville was a pharmacist who developed a test to assess how spicy things were by diluting them in sugar water to varying degrees and then having small panels of testers decide whether or not the test meant anything at all.  Five test subjects tasted the sugar water dilutions and reported whether they could detect any heat or pungency.  The amount of dilution required to make the spicy go away completely for three out of the five became the Scoville score for that substance.

Very, very sciency...

As a scientific test, I suppose it was better than nothing.  For perspective, this was eight years before anyone discovered insulin.  But in the time since the olde-timey year of 1912 when this test was developed, we've invented other more reliable methods of figuring how much of a particular substance is in something.

The current preferred method is High Performance Liquid Chromatography, which yields more consistent, less subjective numbers, but there can still be some variation.  This test doesn't spit out results in the popular Scoville Heat Units, but rather in ASTA pungency units (named for the American Spice Trade Association).

But wait!  Everyone's so used to talking about the Scoville scale!  Maybe we should just keep referring to those units of measure even though they make little sense!  Or at least that's what I assume happened because now someone's figured out an approximate conversion for ASTA units into Scoville units so we can keep happily expressing heat levels in SHU, only now they're more accurately tested SHU, maybe.

So how the hell do you tell WHICH Scoville units you're being given, the old-timey, inaccurate, subjective ones or the newer, still-inaccurate-but-better ones?

As far as I can tell, you can't.

How hot is your favorite sauce, really?  Depends on who you ask.  Depending on the source, the numbers can range all over the place for the exact same sauce.  And I don't think there's a way to tell which numbers are closest to accurate.

You're on your own, everyone!