 Working as an assistant professor in civil department from Molchan Institute of Technology, Solaapur. Today's class, we are going to discuss the ventilation and the functional requirements of a ventilation system. These are the learning outcomes. At the end of this session, students will be able to impart the knowledge of functional requirements of the ventilation system. Ventilation is defined as a process of removing or supplying the air by natural or the mechanical means to and from a air source or any space. Adequate ventilation is necessary. Adequate ventilation is required to maintain the temperature limits inside the building and to remove the air by the products of the respiration and the unpleasant odours. The poor ventilation, it leads to the feeling of uneasy and discomfort to the occupants of the building because it causes the increase in the temperature and the humidity which is due to the increase in the temperature which leads to the perspiration and the sweating. It also causes the sleepiness, the laziness and the inattentiveness. So also an unventilated room, it leads to the unhealthy living and the working conditions because of the increased amount of the dust amount and it may be due to the increase of the amount of the carbon dioxide etc. So also the air which is required for the breathing that is depends upon the use of the building itself. So the amount of the air apart from the supplying the air for breathing, the quantity of the air which is needed, it depends upon the outdoor conditions such as the control of the concentration of the dust particles, the smoke and the extra smoke etc. So let us see the importance of the ventilation, actually it prevents the undue concentration of the body odours, the fumes and the industrial products. It also prevents the undue concentration of the bacteria carrying the particles. It prevents the flammable concentration of the gas vapours or the gas in case of the industrial buildings. It maintains the conditions suitable to the contents of the space. Also it creates a healthy living and the working conditions. It removes the products of the combustion and in some cases it is to remove the body heat, the heat actually which is liberated by the operation of the electrical and the mechanical equipments. So to overcome the living and the working conditions, the comfort of the living and the working conditions, these are the functional requirements of a ventilation system. That is the rate of supply of the fresh air, second is the air movements or the air changes, third is the temperature of the air, fourth is the humidity and fifth is the purity of the air. So the rate of supply of the fresh air, the quantity of the fresh air to be supplied to a room depends upon the use of the building to which it is subjected. So the rate of supplying the fresh air, it actually depends upon the several factors. You can even consider the number of the occupants which they are occupying the building and also the age of the occupants, it depends upon the type of the work which is going to conduct in the building and also the period of the work. Next we have the air movements or the air changes. Air has to be changed actually at places of the working. So air has to be changed due to the, which causes the proper ventilation of the space. So the minimum and the maximum rate of the air change per hour are 1 and 60 respectively. So the temperature of the air, it is desirable that the incoming air for ventilation should be cool in summer and it should be warm in winter before it enters the room and also the velocity of the incoming air if it is high, the temperature should not be lower than the room temperature. Actually the, also the effective temperature within the room, it should be effective so that it should have a comfortable living and the working conditions. So also the temperature difference between the inside and the outside should not be more. The next is the purity of the air. The purity of the air, it plays a significant role in the comfort of the people affected by a ventilation system. It also depends upon the impurities that are impurities that are in the environment. The impurities which are depend upon the habits of the occupants also and even the dust particles, the inorganic matter which is in the surrounding area, the impurities created in the environment. So the purity of the air, it creates a healthy and the healthy living conditions and also it improves the surrounding area. So the systems of the ventilation, actually these are the systems of the ventilations divided into two. That is first is the natural ventilation and second is the mechanical ventilation. So in the natural ventilation, the natural ventilation it allows the outside air to enter into a room through the openings such as the doors, windows and the ventilators. And actually this natural ventilation it is considered to be economical in the flats and the houses. And natural ventilation it is also found to be uneconomical in the office buildings and in theatre halls or the auditoriums and assembly halls etc. So this you can see the outlet and the inlet so that the fresh air it is coming inside to warm up so the natural air. So there are different techniques to achieve the natural ventilation. First you have the stack effect and the wind effect. So this is the wind effect, here you can see that the wind effect actually the ventilation systems are affected by the temperature differences in the wind and due to the velocity of the wind. Actually when you see that it depends on the velocity of the wind. So here you can see when the wind blows the pressure differences are created that is you have a positive pressure on the windward side and a negative pressure on the levered side and when the wind pressure it blows at an angle of 90 degrees you can see that the wind pressure it is created, positive pressure is created on the windward side and the negative pressure is on the levered side. And here you can see that the suction zone it is on the other side. So when the wind comes when the wind flows from the inside and goes through the other side and when the building it is at an angle of 45 degrees so the windward pressure the positive windward pressure is provided is produced on the two windward side and a negative pressure is produced on the two on the two levered side. This is the stack effect the ventilation, ventilation rate is affected by the stack by the stack effect due to the pressure differences and the temperature differences due to the it is also due to the incoming and the upcoming airflow and also it is due to the high difference of the inlet and the outlet also. Here you can see in the figure that the when the temperature is high inside as compared to the outside the warmer air which is inside it goes through the outlet through the outlet so that the incoming air from the inlet it comes inside to warm up the to cool the to cool the inside room this is what the stack effect. So the artificial ventilation the following methods of the mechanical or the artificial ventilation are in the common use. You have the exhaust system, second is the supply system, third is the combination of both the exhaust and the supply system finally we have the air conditioning. So air conditioning is the process of the beating air so as to control the simultaneously is temperature, humidity and to meet the requirement of the conditioned space such as comfort and health of human beings needs of industrial processes efficient working etc. So the purpose of the air conditioning in residential building we can see that it is required to preserve and maintain the health comfort and convenience of the occupants. In case of the industries the air conditioning may be required to preserve the quality of the industrial products and to create and control and maintain the working of different processes such as artificial self cotton cloth etc. and even in the air air airways railways also the air conditioning is provided here you can select the correct answer MCQ is given the term dash is used to mean the free passage of clean air in a structure. You have the options as first is the circulation the ventilation dissipation and condensation this is the right answer ventilation that is due to the ventilation it is used to mean free passage of the clean air so that it replaces the polluted air these are the references which are thank you.