Hazardous materials were frequently used in heritage (objects, sites, and buildings) in the past, both as applications inherent to the heritage (e.g. fireproof asbestos textile) or during restoration and conservation treatments (e.g. pesticides to treat wood against insects). Today, many of these objects have found a second life in heritage institutions and collections, and buildings and sites are opened to a wider public. Although there is increasing awareness of the harmfulness of these materials and substances, this heritage poses a challenge to museum and heritage professionals.