A method of detecting a leakage of a chemical from a closed system into the environment and/or revealing the location of the leakage is provided. The method includes the steps of: placing a test strip in close proximity of or in direct contact with a suspected leak in the closed system, the test strip including a support material and a color forming composition disposed on the support material, the color forming composition including a dye precursor encapsulated in a microcapsule, a developer and optionally a filler; and detecting development of a color on the test strip in response to contact of the microcapsule with the chemical thereby indicating the presence of and/or the revealing the location of the leak.