Is it safe to heat fluorite (CaF2) to 140 °C? For the manufacture of the optical system, we need to heat the fluorite ($\ce{CaF2}$) lenses to $\pu{140 °C}$. Is it possible:


for some poisonous gas to be emitted? ($\ce{F2, HF}$ or other)
for defects to appear on the glass? (scratches, chips, cracks and the like)


If yes, please supply sources describing the corresponding scenarios.
The melting point of $\ce{CaF2}$ is over $\pu{1400°C}$. There is no way $\ce{F2}$ can be generated without electrolysis of the molten $\ce{CaF2}$. $\ce{HF}$ is produced by reaction of conc sulfuric acid on $\ce{CaF2}$. Concentrated $\ce{HCl}$ does react with fluorite to some extend, but the reaction is very slow so, unless your operators drool like the monster from Alien, there is no chance of $\ce{HF}$ formation.