Water-reactive substances, which are defined in international regulations as substances that, in contact with water, release flammable gases, are assigned to USDOT Hazard Class 4.3. The gases released may also be highly toxic. For instance, ferrosilicon, when in contact with water, releases arsine and phosphine gases. The test procedures and classification criteria for Hazard Class 4.3 are inadequate. For example, the procedures and criteria do not take into account (1) water reactions that may lead to the release of toxic gases, (2) the quantity of water-reactive substances being shipped, or (3) the potential effect of water salinity on release of toxic gases.
The objective of this research was to identify test procedures and classification criteria for water-reactive materials (WRMs) that take account of the potential release of toxic gases during transport.