Explosion of pressurised tank during oxygen production

The event occurred at a company producing machines for water treatment for the food industry.
A pressurized tank exploded killing two workers and shaking windows and ceilings at neighbouring companies for blocks around.

The company was developing and manufacturing pressurised tanks used in water filtration system. On the day of the accident, a worker was experimenting with a system designed to add oxygen to water, for farming applications. The system involved was an 80-gallon water storage tank . By starting generating oxygen, hydrogen gas was produced and accumulated in the storage tank. When one of the workers removed the plug from the top of the storage tank, the tank exploded.
The force of the explosion, which fire officials believe may have been the equivalent of two or three sticks of dynamite, killed both workers instantly and forced the evacuation of company and two adjacent businesses sharing the 10,000-sq. foot building.
It is plausible that the workers were unsuccessfully attempting to separate hydrogen and oxygen before feed the oxygen to the water. probably too much hydrogen was fed to the tank together with the oxygen, developing an explosive atmosphere which ignited when opening the top of the tank. Apparently the technology, which allows farmers to feed farm animals oxygen-enriched water, has been around for the last four or five years.
(this is the News report, see also OHSA report under References).

INITIATING cause is the opening of a tank containing hydrogen.
Although the OHSA report does not provide a root cause analysis, a plausible cause is operational, considering the complete lack of preventive measures such as flammable gas detection.

pressurized tank, oxygen-enriched water system

Two men were attempting to separate hydrogen and oxygen from a 80-gallon tank filled with water inside a research laboratory-warehouse area.
The technology allows farmers to feed farm animals oxygen-enriched water.

Despite the presence of corrosive acids, oxygen and hydrogen in tanks near the explosion. No other tanks were ruptured.

The OHSA investigation imposed fines in the order of magnitude of $ 10000