An indicator device and method for monitoring disinfection or sterilization of closed environments and surfaces located in said closed environments, the disinfection and sterilization made by applying a disinfection or sterilization agent, wherein the indicator device comprises a carrier coated or embedded with substances or reagents that produce a change in color or in other readily visible property when contacting said disinfection or sterilization agent, and wherein the carrier is configured as a polyhedron, a cone, a cylinder, a sphere or any three-dimensional shape. A planar carrier having weakened linear areas or groves, printed lines or printed images, and so it is configured to be folded along said linear areas, groves or printed lines or images so as to form a polyhedron, a cone or a cylinder and so it is configured to be folded along said linear areas, groves or printed lines or images so as to form a polyhedron, a cone or a cylinder.
