Combustible Concealed Space Upright Sprinklers TY2199 (Model CC3) 4.2 K-factor are quick 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 Model CC3 Sprinklers comply with the criteria for the protection of combustible concealed spaces as described in NFPA 13.