Acknowledgements
We are indebted to Prof. Dr. Thomas Gebel at the Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, who checked our computations and advised us of this error.
Declaration of interest
This work was funded by the HTIW Coalition, which represents producers of RCF and other high temperature insulating fibers in North and South America, Europe, and Asia. The findings and conclusions of this paper are those of the authors alone.