To resolve a problem of coolant such as ethylene glycol which has high cooling performance but also danger of burning when exposed to high temperatures, has toxicity and contaminates the environment when flowing out to the ground, diverges an unpleasant odor therefrom and drifts along with an air flow, to prevent burning even when it is exposed to high temperatures, to eliminate its toxicity and to prevent harmful effects to the environment even in treatment after usage.

A 40-50% aqueous solution of lactate is sealed in a sealed container using a flexible watertight sheet.