Abstract: Abstract: The CO2 concentration is required to be below 1500 mg/m3 (Environmental Quality Standards for the Livestock and Poultry Farm of China, published in 1999) in layer hen houses where the manure is disposed by powered scraper, the litters generally need to remind and the drinking device has water leak. Consequently, moisture and NH3 levels in such barns are much high. Also, air temperature is much lower in winter, because the minimum ventilation rate is large in winter. However, the manure is cleaned daily in new poultry house with manure convey belt. Meanwhile, the aerial pollutants (CO2 and NH3) are reduced and the relative humidity is decreased. Indoor air quality in this kind of poultry house is dramatically improved. A new standard of CO2 concentration and the minimum ventilation rate of layer house with manure convey belt should be reconsidered. Determining the CO2 concentration standards for the manure convey belt in layer hen houses is needed. The objectives of this work were to draw a conclusion about the CO2 concentration levels and use it as a reference to calculate the minimum ventilation rate in winter. This review summarized the recent measurements of the emission rates of aerial NH3 and the CO2 concentrations in poultry houses in which the laying hens were kept in cages. The relationship between CO2 and NH3 was also described based on the data got in the poultry houses with different manure removing way from the domestic and foreign study. In addition, the minimum ventilation rate is important for ensuring the ideal air quality in poultry house in winter. The optimum ventilation is one of the factors affecting poultry production and energy consumption. Considering the mass conservation under steady-state conditions in the layer hen building, there are 2 main sources of CO2 in poultry house, and most of the CO2 is produced by respiration processes of layer hens, if neglecting the amount of CO2 emitted from manure. The minimum temperature value for layer houses was 13 ℃ in this study. The following conclusions were drawn in this study: 1) There was a positive and significant correlation between CO2 and NH3 concentration in layer houses based on analyzing the data of previous researches. The standards of CO2 concentration and NH3 concentration were suggested to be 5000 mg/m3 and less than 15 mg/m3 respectively in the layer hen houses with manure convey belt. This condition would not reduce the hen's performance and defenses. Primary CO2 concentration standards persisted when the feces were scraped by powered scraper to a cross conveyor at the end of the barn; 2) Average NH3 concentrations in the layer house with manure convey belt was largely less than the traditional house with the scraper. Therefore, rebuilding new layer hen's building equipped with the manure convey belt is crucial not only for indoor environment, but also for ventilation system; 3) Ventilation rate was calculated using the rate of laying hen in winter based on CO2 mass balances from the literature. The constantly minimum ventilation rates were 0.40-0.50 m3/(h·kg) for the layer houses with manure convey belt. The new standards of CO2 concentration and ventilation rate were beneficial for improving indoor environment control and ventilation energy efficiency, and saving constructional costs. Furthermore, the results of this paper provide the reference for solving the contradiction between ventilation and insulation system in layer house. Also, it can improve the versatility of poultry environment and provide the support for emission studies using the new standard of the CO2 to evaluate the poultry building environment.