The specified value describes the building material class according to DIN 4102-1.
A1 = non-combustible, without parts of combustible building materials
A2 = non-combustible, with small proportions of combustible building materials
B1 = flame retardant
B2 = normally flammable
This classification according to DIN 4102-1 is still valid until further notice, even though the standard is gradually being replaced by the European standard DIN EN 13501-1. Newly launched building materials and products are therefore no longer classified according to DIN 4102 but according to DIN EN 13501.
Source: bauwion
