Orange silica gel turns green as it adsorbs moisture, indicating the need for reactivation or replacement. Prevents the formation of mould, condensation and rust in enclosed spaces. Orange indicating silica gel is ideal in applications where visual control of moisture is required. The silica gel will turn from orange to green as it adsorbs moisture, indicating the need for reactivation or replacement. Silica gel works by adsorbing and trapping moisture from the air, lowering humidity and preventing the formation of mold, condensation, and rust in enclosed spaces.