Table 14.6.

CO2 concentration exposure categories suggested for diffuse degassing hazard maps (Viveiros 2010)

Soil CO2 concentrationEffects
CO2 vol%<1.5Low risk of asphyxia
CO2 concentrations are those of non-volcanic areas.
1.5<CO2 vol%<5Moderate risk of asphyxia
Spaces below ground or non-ventilated areas may accumulate lethal concentrations.
CO2 vol%>5High risk of asphyxia
Lethal concentrations can be reached in basements and/or non-ventilated spaces below ground. Lethal concentrations were measured at ground level (20 vol%).