The invention relates to a chemical indicator composition comprising a bismuth (III) oxide elemental sulfur and a compound which makes the composition alkaline when exposed to water vapor at an elevated temperature, said compound having a solubility in water at 100°C of not more than 1 gram per 100 cubic centimeters of water and/or wherein said compound is selected from sodium carbonate, sodium bicarbonate, barium hydroxide, lithium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, calcium hydroxide, magnesium hydroxide, sodium acetate, potassium salt of 2,4-dihydroxybenzoic acid, a potassium salt of 2,4,6- trihydroxybenzoic acid, a lithium salt of 2,4-dihydroxybenzoic acid, a lithium salt of 2,4,6-trihydroxybenzoic acid and a combination thereof, and wherein the bismuth (III) oxide and elemental sulfur are present in a weight ratio of 0.5:3 to 2:3 and wherein the elemental sulfur and the compound which makes the composition alkaline are present in a weight ratio of 1:5 to 1: 1.
