Fluorine can be evolved during the firing process of  ceramic raw materials. This gas is toxic both to humans and the environment as a whole. Careful control of kiln firing can trap most of the fluorine in the ceramic matrix. It is advisable to scrub exiting kiln gasses to remove the majority of the acidic gases, including fluorine, sulphur dioxide, etc.

Pyrohydrolysis technique

This involves fine grinding the sample and mixing it with a catalyst, normally vanadium pentoxide. This mixture is placed in a furnace maintained between 900^oC and 980^oC. Steam is passed over the sample and the liquor collected is tested using an ion selective electrode technique.