See Brief request syntax to understand each keyword.
CAMS GFAS Wildfire Flux of Carbon Dioxide Analysis Example
co2fire parameter in NetCDF format, January 2003. ECMWF Public Dataset web interface
#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
"class": "mc",
"dataset": "cams_gfas",
"date": "2003-01-01/to/2003-01-31",
"expver": "0001",
"levtype": "sfc",
"param": "80.210",
"step": "0-24",
"stream": "gfas",
"area": "70/-130/30/-60", # N/E/S/W area boundaries
"target": "cams_gfas_co2fire.nc",
"format": "netcdf",
"time": "00",
"type": "ga",
})