Abstract: The objective of this study was to investigate harmful gases concentrations of dairy cow houses in winter in the chill region of Hebei province.Three styles of dairy cow houses and four styles of calf houses in Bashang plateau in Hebei province were used in this study to determine NH₃ and CO₂ concentrations.The results showed that the CO₂ concentrations were extremely significantly higher in well-closed dairy cow houses than that with exercise yards (P < 0.01).And the CO₂ concentration in the evening was higher than that in the morning and at noon,reaching up to 4 481.7 mg/m³(dairy cow house 1).The CO₂ concentrations in all calf houses were high in the morning and evening and low at noon.Besides,the CO₂concentrations in all dairy cow houses and calf houses were extremely significantly or significantly higher than that in the net roads or exercise yards (P < 0.01;P < 0.05).The NH₃ concentration of three dairy cow houses showed a sharp rise trend after 19:00 and the dairy cow house 3 only detected the low concentration of NH₃ which ranged from 0 to 0.36 mg/m³.The NH₃ concentration of the calve houses were changing from 0.71 to 5.28 mg/m³.In conclusion,the harmful gas concentration related to the building types and structure that CO₂ and NH₃ concentration were higher when the cowsheds were sealed,even exceeded standard badly.To reduce the harmful gas content in the house,the ventilation should be taken into account to improve the air quality.

Key words: dairy cow house; calf house; harmful gas; building type; cowshed design