Range of methane & CO2 concentration on landfill surface

I am interested in starting an academic project on landfill methane monitoring and modeling. If I want to carry out a surface monitoring (maybe using flux chamber), then what should  ideally be the range (in ppm by volume) of my methane and carbon di-oxide analyser? In other words how much maximum methane gas concentration (in ppm) is expected to come out of landfill surface? I am from India and the conditions are absolutely suitable for anaerobic digestion (warm, humid and the municipal solid waste constitute approx 50% organics).

Oil and Gas Research Equipment Environmental Geotechnics