A note about knee jerks. Don't ask a manufacturer if it's safe to fly in ash...
A corollary to that: never ask "is it safe to..." from any regulator or official of authority, because the easiest answer is no, absolving said official from any blame whatsoever if something should go wrong, irrespective of any causal effect. The correct way to ask is "what is the acceptable limit to...", forcing the regulator to at least provide some reasoning.