Emission of greenhouse gases (GHGs) from mechanically ventilated deep pit manure storage was monitored in a swine gestation operation. Air samples were collected from pit exhaust fans at different times of the year (fall, summer, and spring) using a vacuum chamber and Tedlar bags. GHGs concentrations were measured with a greenhouse gas chromatograph (GC) within 24 hours of collection. Air flow rates from exhaust fans were measured using a 160 mm bi-directional Gill propeller anemometer and the ventilation rate was determined as the summation of air flow rates from all fans. The average methane (CH4) concentration was 88±61 ppm and CH4 concentration differences were statistically significant among sampling dates and seasons. The carbon dioxide (CO2) concentration followed the same trend as CH4. The average CO2 concentration was 1105±1063 ppm. Nitrous oxide (N2O) concentrations ranged from 0.02 to 0.66 ppm. Methane emissions varied between 115.94 to 572.18 g d-1 AU-1 and higher methane emission was observed during summer (480.28 g d-1 AU-1). The average carbon dioxide emissions varied from 5.35 to 15.83 kg d-11 AU-1, whereas average N2O emissions varied from 0.06 to 7.30 g d-1AU-1. Significant variation of GHG concentrations and emissions were observed among fall, summer and spring seasons. Read more..