الفهرس 
Thermal environment affecting a biological system.
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Abstract
Environmental control inside the agricultural structure is considered as one of the most important factors affecting productivity of protected cropping, animal, and poultry. Agricultural structures such as livestock and poultry housing and greenhouses,... etc» should have the capability to offer the optimum environment for the confined biological system. One of the most important environmental factors that affect a confined biological system is temperature. As well known, there is a thermo-neutral (comfort) zone for each biological system, so that chagrining of temperature beyond the maximum or minimum limits of that zone depresses productivity. However, an environmental control system may be needed to keep the required comfort zone inside the structure. from the viewpoint of thermal environmental factors, an environmental control system may be used as an auxiliary system to control the temperature within the comfort zone via heating or cooling process. Egypt has a climate tend to be warm or hot throughout the most of the year months. Therefore, heat stress is considered as an accompanied problem that the biological system such as poultry or dairy animals can be exposed to. Such problem could be noticed clearly in summer months and during hot waves throughout the year. As well, it obviously appears in broiler houses with intensive production specifically before marketing increasing percentage of mortality. Accordingly, searching for a simple or not sophisticated system to cope with the heat stress problem inside the agricultural structures is needed.