Deuterium Gas D2 UN1957 Deuterium is also known as “heavy hydrogen” due to the added mass of the neutron. It is used in a variety of applications, ranging from university and industrial research comparisons between the hydrogen and deuterium in deposited film analysis, to use as a rapid thermal anneal for certain semiconductor devices where hydrogen’s lighter mass is not desired. Deuterium is a highly flammable and asphyxiant gas.