In rubbish dumps, due to organic substances decomposition, methane, sulphured hydrogen, and carbon dioxide can be generated. Often, these gases find a way through the layers of ground up to reclaimed areas where there might be buildings.

GASES INVOLVED

Oxygen (O2): meant as lack of oxygen is caused by the massive presence of other gases.
Methane (CH4): it is the result of the decomposition of some organic substances in absence of oxygen. It is considered a biogas.
Carbon dioxide (CO2): it is a transformation product of every decomposition process.
Sulphured hydrogen (H2S): it is a sub product extremely present in all the places where rubbish is collected.

EXPECTED RISKS

O2: both excess and lack of oxygen may cause important diseases, sometimes death.
Inflammable gases: in smaller concentration even than LEL with regard to the volume they explode in presence of a minimum flash source often resulting in serious consequences for people and things.
CO2: poisoning due to carbon dioxide, risk of asphyxia due to lack of oxygen.
H2S: colourless gas stands out for its characteristic smell of rotten eggs. A low-concentration exposure causes eye and throat irritation, cough, acceleration of breathing and fluid formation in the respiratory
ways. High concentrations kill the olfactory nerve so making impossible to smell its disgusting odour, and may cause unconsciousness in few minutes.