Combustible Concealed Space Upright Sprinklers TY2189 (Model CC3) 4.2 K-factor are fast response, upright, specific application sprinklers designed to provide protection of specific light hazard combustible, as well as non-combustible, concealed spaces requiring sprinkler protection. The CC2 Sprinklers comply with the criterion for the protection of combustible concealed spaces as described in NFPA13.