Barium Carbonate is primarily used as a colorant to produce green hues in pyrotechnic compositions. When heated or ignited, it decomposes to release carbon dioxide and Barium Oxide, which react with other materials in the pyrotechnic composition to produce green flames and sparks.
It can also be used as a fluxing agent to reduce the melting temperature of other pyrotechnic materials, making them easier to work with during the manufacturing process.
One of the benefits of this is that it is relatively safe to handle, making it a popular choice among pyrotechnic manufacturers. However, it can be hazardous if ingested or inhaled, and should be handled with care to avoid accidental exposure.
Most barium compounds are very poisonous, especially the more soluble barium compounds such as the chlorate and nitrate. A dust mask should be worn at all times when working with barium carbonate. Unlike its soluble cousins which can be easily washed from the hands with lots of water the carbonate is not so easily removed and care to remove the powder from under fingernails is important before eating etc. Barium carbonate is soluble in stomach acid, and therefore a poison by ingestion.