WSH Alert – Workers Killed by Acid Burns

Incident
On 27 Feb 2009, a group of workers were pumping nitric acid (70% concentration) into a heat exchanger to remove some residual polymer (di-methylacetamide). During the process, a reaction occurred within the heat exchanger. The reaction most likely generated heat and gases and caused pressure to build up inside the tank. Consequently, the contents of the heat exchanger was forced out and toxic fumes were also emitted. The mixture splashed onto the workers, killing 4 and injuring another.

Recommendations*
1. It is important for the Management to show commitment and put in place an effective workplace safety and health management programme. Through this, operations within the organization would be guided through a safety policy, establishment of a safety management system and proper work procedures.
2. A risk assessment must be carried out before starting any work. This is especially important for new or unfamiliar work, operations or processes. Through the risk assessment, employers and workers can identify potential hazards and take appropriate actions to eliminate the hazards or reduce the risks involved. Control measures and safe work procedures must be established and implemented to ensure the safety and health of the workers involved.
3. All hazardous substances in the workplace should be placed under the control of a competent person who has the adequate knowledge of the properties of the substances used and their associated dangers. A course, such as the “Management of Hazardous Substances” conducted by the Singapore Environment Institute provides the necessary training and knowledge in handling such hazardous substances.
4. The National Environment Agency (NEA) requires that any person who wishes to purchase, store and/or use hazardous substances (such as nitric acid) that are regulated under the Environmental Protection and Management (Hazardous Substances) Regulations must obtain a hazardous substances permit. For more information on obtaining the permit, please refer to NEA’s website HERE.
5. In addition, under the Fire Safety (Petroleum and Flammable Materials) Regulations, if petroleum or flammable materials are imported, transported or stored beyond the stipulated exemption quantities, a Petroleum & Flammable Materials licence, issued by the Singapore Civil Defence Force (SCDF), is required. For more information on obtaining the licence, please refer to SCDF’s website HERE.
6. When hazardous substances are used, handled or stored in the workplace, it is necessary to obtain the Safety Data Sheet (SDS) of the substances. The SDS provides key information on the properties of the substances and the hazards as well as the necessary precautionary measures. A copy of the SDS should also be made available to persons who are likely to come into contact with the substance.
7. For any work process that involves two or more substances coming into contact with each other, it is important to always check for the compatibility of their chemical properties. Incompatible chemicals can cause reactions that could result in adverse outcomes such as a fire and/or explosion. If in doubt, you should always refer to the SDS or clarify with the suppliers / manufacturers of the substances.
8. Whenever practicable, containers of the substances should be affixed with easy to understand labels that provide information of the hazards of the substances and the required precautionary measures.
9. A written emergency response plan should be established. Emergency response equipment should be kept on site and made readily available. Personnel responding to such emergencies should be properly trained on the emergency procedures and the use of equipment.

(From WSH Alert dated 5 March 2009)