Because of the importance of emissions from fires in biomass fuels globally, we developed a highly portable Fire Atmosphere Sampling System (FASS) for sampling smoke emissions. Emissions were sampled with the FASS packages from a variety of fuel and combustion conditions in Canada, the United States, and Brazil. The ratios of emissions released for boreal, upland hardwood, savanna, and tropical fuel types are being studied in more detail in our controlled environment combustion laboratory. The FASS employs an onboard computer to control sampling protocols of sensors for measuring the fire, environment, and operating parameters. The system measures in real time the concentration of CO, CO2, NO, and O2; temperatures at several locations; and vector wind. Grab samples of particulate matter and trace gases are collected over specified sample periods of flaming and smoldering combustion. Emission factors, combustion efficiency, source strength, rate of fuel consumption, and rate of heat release are calculated from the measurements.