Citing initial findings from a fatal explosion in July, the U.S. Chemical Safety Board (CSB) – a federal safety agency – has issued a warning to companies with storage tanks.

CSB investigators sent water samples from an exploded tank at the Omega Protein facility in Moss Point, Miss., to a lab for testing. Those tests revealed microbial activity in the samples and off-gassing of flammable methane and hydrogen sulfide.
The explosion at the Omega facility occurred during hot work and resulted in the death of one contract worker and severe injuries to another contract worker. The water inside of the tank had been thought to be nonhazardous, but no combustible gas testing was done on the contents before the hot work started.

The CSB says has now investigated three fatal hot work incidents since 2008 involving biological or organic matter in storage tanks. The Board says companies, contract firms and maintenance personnel should know that inside a storage tank, what might seem to be non-hazardous organic material can release gases that cause the vapor space to rise above the lower flammability limit. When that occurs, a small spark or even heat from hot work can be enough to cause an explosion.

Read entire article - http://www.csb.gov/csb-chairperson-moure-eraso-warns-about-danger-of-hot-work-on-tanks-containing-biological-or-organic-material/