It is used as a preservative to protect specimens against contamination by micro-organisms during storage and, hence prevent them from rotting. These bacteria, yeasts and moulds are always present in the air around us and even in the water we drink. Without preservatives, museum specimens, just like food, can become contaminated, leading to spoilage and decomposition.

It is used extensively for embalming and tanning organic materials.

(Plants and animals also produce Formaldehyde. It is even emitted in minute quantities as a by-product of certain vegetables, such as Brussels sprouts and cabbage, when they are cooked).