Effectiveness of improvised gas absorption techniques for emergency responders at releases of toxic gases

During accidental releases of toxic gases emergency responders use different measures to eliminate the threat of a toxic gas cloud. Case studies from incidents in Vienna or in Trieben in Austria showed the need for studies on the effectiveness of such measures. An Trieben in 2009 IBC tank with 1,000 l of nitric acid (53%) was flipped over by a forklift and cracked open in the top area. The content was fully released and lead to serious corrosion effects on storage racks combined with the production of critical amounts of nitrous fumes. A storage and chemical handling area of several hundred square meters was filled by nitrous fumes with concentrations of up to 100 ppm. Emergency responders used an improvised gas absorption system to clear the area of toxic fumes. Outside the sealed area concentrations of nitrous fumes well below the AEGL-2 (4h) value for nitrous dioxide where measured. In the course of the analyses of the response, the effectiveness of improvised gas absorption techniques was investigated. For the investigations, chlorine and ammonia in combination with a mobile exhauster, (10,000 m3/h) commonly used by emergency responders in Austria were used. Different methods of gas absorption were investigated and tested on their practical relevance. © 2014 American Institute of Chemical Engineers Process Saf Prog 34: 154–156, 2015