In BS EN 12150-1: 2015: Glass in building – Thermally toughened soda lime silicate safety glass, a fragmentation test determines whether the glass breaks in a manner prescribed for a toughened glass.  Following breakage of a sample of size 360 mm x 1100 mm, a particle count is carried out over an area of 50 x 50 mm in the coarsest region.

For 4 to 12 mm toughened glass, the minimum particle count in BS EN 12150-1 is 40.

For more specific details, please refer to the standard, BS EN 12150-1: 2015: Glass in building – Thermally toughened soda lime silicate safety glass. (www.bsigroup.com )