A container which is useful for safely storing and transporting compositions, such as liquid organic peroxide-containing compositions, which may be flammable, combustible, susceptible to exothermic decomposition, explosive and/or otherwise hazardous, is provided. The container includes a containment vessel having thermoset polymer-containing walls, as well as a vent mechanism. The containment vessel may be manufactured by a rotational molding process using a thermoplastic polymer, such as a polyethylene, which is crosslinked to provide the thermoset polymer.