Gas, not slurry, is the real danger when it comes to tank dangers

Michael Flynn’s letter on escape routes for slurry tanks (Sept 19) makes a number of very valid points on escape routes and designs for slurry tanks.

These are very valid for open tanks and lagoons, however, drowning is not the only issue. The Spence family died in only about four feet of slurry. This is shallow enough for most adults to be able to stand in and wade toward an escape route, but the killer in this instance was due to gas in the area.

The biggest danger with underground tanks is not drowning but lack of oxygen. The breakdown of manure like other organic waste (septic tank for house or in council water treatment plant) creates gases; during the time animals are housed the gas escapes in small amounts. When the animals are not being housed the top of the slurry hardens as there is no longer waste falling into the tank, and forms a crust trapping the gas under it. When it comes to emptying the tank the crust is broken and the concentrated gas escapes.