I need to do a mea culpa here.
The NSF 51 standard essentially describes criteria a commercial/industrial material must conform to if it comes into contact with a material intended to be ingested. For tubing specifically, typical examples are food/water/medicine/chemical transport and storage and delivery, air conditioning/furnace drainage, laboratory and medical activities, bottling, and many more.
When I investigated a replacement for the Arizer PVC a few years ago, I looked at other choices as sold by McMaster-Carr, US Plastics, Amazon, etc. and found that all had a temp tolerance up to 500F. To be perfectly honest, I don't recall how the Klearon K010 got lumped in with these. Materials conforming to NSF 51 can acceptably vary in tolerances, depending on the material and its application. When looking again today for the Klearon spec, the only K010 I could find is Series 73. I don't know if that is exactly the same that was used when I bought the Q or if this is what Arizer currently uses. However, what is certain is that at least the Series 63 K010 temp tolerance is 150F, which is obviously far lower than 500F. I have to presume that I erred somewhere.
But before panic sets in, a couple of things to keep in mind: First, the temp at the tubing is
significantly lower than the Q's heater setting. The second is that a material softening or even breaking down does not automatically translate into "leeching"; while it may not be suitable for its intended use any longer, it's not necessary harmful.
So for perspective I set up a test using my IR gun, with the Q set to 500F for 1 hour followed by Fan 3 running for ~20 minutes. At that point I took these readings:
Heater exterior = 300-425F (a wide range depending on where the beam is pointed, with the 425F looking down the center airway opening)
Cyclone bowl = ~350F
Glass elbow = ~220F
Elbow glass connector with PVC fully attached = ~170F
Tubing 1-2" from connector = ~130F
Tubing 6" from connector = ~100F
Tubing 12" from connector = ambient (so vapor entering the bag will drop to ambient very quickly)
While the tubing was still within spec, it did soften considerably just after the connector although it still maintained shape. I was surprised at how fast the heat dissipates. In any event, even sustained at full throttle, the tubing never reached its upper heat tolerance.
I also took the readings without the fan running: The whip did not rise above ambient.
Bottom line: The stock PVC works OK and is safe, but NSF 51 silicone is vastly superior (and costs more, too).
Hopefully the above is satisfactory penance for my error.