[x]

Do not enter manure pits without either: A self-contained air supply like those fire fighters use. (Dust masks or other cartridge respirators will not filter out the toxic gases nor will they provide the oxygen requirement to work in confined spaces such as manure pits.) OR Test before entering. Test the oxygen level to make sure that adequate oxygen is available. Also test for hydrogen sulfide, a particularly toxic gas, to be sure that concentrations are safe (less than 10 ppm).

[Sans-Culotte]

Thanks. I had never heard of this danger but it seem utmost caution is required.