The following is a very general explanation of why Low Free Silica abrasives are important to choose over those with free or crystalline Silica:
Silica occurs in three major forms: Amorphous, Microcrystalline, and Crystalline. The form of silica that needs to be scrutinized for health concerns is the "crystalline silica" also known as "free silica." Crystalline silica which causes silicosis occurs as quartz, cristobalite, or tridymite and as such it is the levels of these specific forms of crystalline silica that need to be determined and scrutinized. Regular sand usually contains very high concentrations of these dangerous forms and this is the reason why such stringent safety measures are required if an operator does choose to use a regular Silica sand.
Silicon and Oxygen make up around 75% of the earths crust, so geologically speaking, SiO2 is actually an exceedingly common compound and can be found virtually everywhere. The first line of the Patriot Blast MSDS showing SiO2 (Silicon Dioxide) levels of 41-53 % refer to non crystalline or free Silicon Dioxide (ie- amorphous silica) and as such this is not the harmful compound that is associated with Silicosis.
ERI is committed to producing the highest quality Silica free products and we are confident that you will find that our products will meet and exceed your expectations.