The current field study was applied on two available different broiler environments (closed and open houses) during winter season in two differed localities, AlJuaymah (NE) and UmSahik (NW) to Ai Dammam city. A total of 20500 and 6850 birds of Rose-308 and Cobb-500 breeds respectively were used to study the effect of different broiler environments on their indoor air quality and the microbial ecology of air and litter started day before baby chicks admission up till marketing. The indoor air parameters included ‘Ta.C°, RH % ,AVm/sec) , some gases (CO, and NH3 ppm) and microbial load of air and litter fungal and bacterial colony forming units, cfu counts/m3 and cfu/ gm respectively).The results revealed the following: During winter season the closed system seemed to be more suitable for brooding baby chicks regarding to controlled indoor Ta C°, RII % and AV m/sec, despite the expected gases accumulation for keeping warm environment and increased litter microbial feed and air fungal load that represent risk factors for both birds and their keeper .The obvious effect of indoor air parameters (positive correlation except CO, showed negative one) and litter microclimate on microbial loads in both environments threw light on efforts must be done by owners and ever alerts to follow up , manage and alternate the indoor conditions for controlling indoor microbial niches , starting before chicks admission till marketing to keep indoor and outdoor livings health Open system characterized by significantly lowered indoor at parameters levels Vs closed system Indoor Ta .C* showed positive correlation with litter of cfu: only , While RH %, CO an NH, were positively correlated with air and little microbial load