In Denmark, the emission rate of methane from dairy cows has been calculated using the IPCC standard values for dairy cows in Western countries, due to the lack of national data. Therefore, four respiration chambers for dairy cows were built with the main purpose of measuring methane, but also emission of carbon dioxide, hydrogen and consumption of oxygen. The chambers are constructed of steel and polycarbonate. The outside dimensions of the chambers are 183 × 382 × 245 cm, and the volume is approximately 17 m³. The air inlet is a small gap between the floor and bottom of the chamber. The air outlet is placed at the top of the chamber. The flow rate in the chambers is measured with a mass flow meter. The concentration of gases is measured every 12 minutes with a chemical hydrogen sensor, a paramagnetic oxygen sensor and infrared carbon dioxide and a methane sensor. The ventilation rate for dairy cows is between 800 to 1500 L/min depending on the milk production and liveweight. This gives an average concentration of 5000−6000 ppm of carbon dioxide and 500−600 ppm of methane in the chambers.
Technical Manual on Respiration Chamber Designs, 2012, p. 61-79