In an uninsulated livestock building with natural ventilation, the air temperature and airflow show a large variation according to the daily variations in weather and season. The objective of this investigation was to determine the diurnal variation in the emission of NH
, CO and moisture from an uninsulated building with a deep litter system for growing/”nishing pigs and to investigate the in#uence of air temperature and air#ow rate on the NH
emission. The investigations were carried out in an uninsulated experimental building with 125 growing/”nishing pigs in deep litter pens. The building was 12 m wide and 20 m long (240 m), naturally ventilated but also equipped with exhaust fans. TheNH
concentration, the CO concentration, the outside and inside air temperature, the outside and inside relative humidity and the animal activity were measured continuously during 6 days at a constant air#ow rate of 146 m
m h. During six nights the e!ect of air#ow rate on the NH
emission was investigated by changing the air#ow rate in steps from 26 to 165 m
m h. The measurements were carried out between day 16 and day 46 from the beginning of the growing period. The
NH
emission from an uninsulated, deep litter building for growing/”nishing pigs showed a clear diurnal variation. During the 6 days with constant air#ow rate the emission varied from 6 to 247% of the mean, with the minimum around 6.00 a.m. and the maximum around 5.00 p.m. The daily mean ofNH
emission increased from 0)23 to 0)65 g h per pig (day 16}day 43). The diurnal variation of NH
emission was correlated to the inside air temperature (correlation coe$cient r
”0)86}0)91) and the animal activity (r
”0)69}0)83). The increase of NH
emission with the air temperature followed an exponential pattern. The relative NH
emission #ux increased from 0)2 to 2)0 between the air temperatures!2 to 143C inside the building. An increase in air#ow rate through the building from 26 to 165 m
m h increased the relative NH
emission #ux from 0)4 to 1)4. The CO emission during the 6 days at constant air#ow rate had a daily mean between 81 and 120 g h per pig with a diurnal variation from 61 to 249% of the mean. The CO emission was correlated to the inside air temperature (r
”0)42}0)83) and animal activity (r
”0)67}0)85). The daily mean of water vapour emission increased during the same days between 146 and 408 g h per pig and varied from 18 to 269% of the mean. The
water vapour emission was correlated to the inside air temperature (r
”0)53}0)97), animal activity
(r
”0)57}0)85) and the water absorption capacity of the inlet air (r
”0)27}0)94). The diurnal variations in NH
, CO and water vapour emission were correlated to each other.