The Difference in Using a Positive Pressure Ventilation Fan to Fire Service - Lab Report Example

Abstract A series of experiments was done in a model house to find the ability of Positive Pressure Ventilation fan service to limit the spread of smoke or removing smoke from areas where there is chance for occupants to be located. The experiment was repeated under natural ventilation also to understand the difference in using Positive Pressure Ventilation fan to fire service. The preliminary experiment was done to find the use of Positive Pressure Ventilation fan by placing it in front and the experiment was repeated again in rear. The size of the fan and the distance from the entrance of the house was changed to understand more the usage of Positive Pressure Ventilation. The main fire scenario included a model house that had a front door, front room, back room, and back door and the experiment was conducted using fans of three sizes, smoke pellet, stop watch and lighter. The scenarios included producing large amount of smoke that was produced by fires and instrumentation was placed to understand how the natural ventilation and PPV fans are helping to understand the fire extinguishing tactics. The measurements included the finding of temperature, pressure and so on. The experiment is conducted broadly to understand the conditions that can be improved for fire fighting crews so that the life of potential victims can be saved. Introduction Aim and objectives The concept of natural ventilation and how positive pressure ventilation (PPV) may impact the fire fighting was put to test and how the various positioning of the devices and how the change in size of the fan is going to help the positive pressure ventilation. The full scale results are used to provide more insight into the size and positioning of the gadget. The guidelines that will be developed will be to make the effective use of positive pressure ventilation. Background What is Positive Pressure Ventilation? Positive pressure ventilation has been used to remove smoke, heat and other combustion products from a structure and this has been used by fire servicers .The idea is to create an environment where the other activities of fire service men is done in an efficient manner. It is creating a situation by which the fire is made difficult to advance and spread.( Rimen ,2000) The fans are positioned in such a manner that the cone of the air is produced and that helps the pressure to extend beyond the opening. The air pressure inside the room is increased and an opening in the roof or an open window can help the pressured air to escape due to the difference between the inside and outside pressure. The pressurized air that is removed will remove the smoke heat and other combustion products and will allow the fresh air to come in. History of Positive Pressure Ventilation The positive pressure ventilation was first developed in United States in the year 1960 and it was used on a limited basis on the fire fighting department. It was in the 1990s, the information about the usage of positive pressure ventilation which was widely available and research studies was done to understand the benefits that the fire fighters got and positive pressure ventilation has been accepted by fire departments and fire brigades all over the world. The benefits PPV has been found to remove the heat and smoke from the building very fast. The atmosphere is improved faster so that the patient survives.( Svensson, S.,2001)The search operations and the rescue operations can be conducted in an atmosphere devoid of smoke.( P.S. Ziesler, 1994) The atmosphere will be improved with increased visibility and the fire fighters are given the safety of doing the extinguishing operations. The heat and the stress are also removed and can reduce the risk of roof and ventilation at many fires. The level of Carbon Dioxide and other toxic gases are removed and positive pressure ventilation also removes the chance for flashover. The main points to be kept in mind For PPV to be effective, it has to be applied properly and for that to happen an opening for the pressurized air has to be provided and that opening which can be termed as exit should be in the place of occurrence of fire. This opening can be in the form of window or any other opening. The positive pressure ventilation should be applied from the unburned side of the fire and that means the opposite side of the fire. The sealing of one area should be done as the smoke is removed fully and another exit will be created in another part so that the air flows into that area. Materials used for the experiment The experimental setup included a front door and rear door and the rooms were divided into front room and back room. Both the rooms were not similar as the back room had a staircase to the top and there was door that can be opened at the top. On comparison, the front room appeared to be smaller in size compared with the back room. The inlet to the building can be said as the front door and the front room can be opened to the second room titled the back room. The figure shows the position of the back door and the positions of the doors are in straight line. The experiments are to be conducted in the front room and the back room. The door on the top is not to be used for the experiment. Three fans of varying specifications are used for the experiment. The first fan can be said as the small fan and had the following specifications of fan blade diameter as 60 mm with the blade length as 12 mm and the outer measurements being recorded as 60 mm *60 mm*25 mm thickness. The velocity was measured through cylindrical tube and it has been measured as 1.91m/s. The second fan be simply termed as large fan. The blade diameter was measured as 75 mm and the blade length has been found as 23 mm. The outer measurements has been found as 80 mm*80 mm* 25 mm thickness. The velocity was measured through cylindrical tube and it has been measured as 2.03 m/s. The third fan can be termed as large fan with red support frame. The blade diameter of the fan was measured as 75 mm and the blade length has been found as 23 mm. The outer measurement has been measured as 80mm*80mm*25mm thick. The velocity that was measured using cylindrical tube and it was measured as 2.61 m/s. The methodology of experiment The first test was done on natural ventilation. Before the test is started, all the external doors and windows of the house are closed and in this case the front door, top door and the rear door are closed. The internal door between the front area and back area is kept open at the time of experiment. The smoke pellet will be placed in a metal tray at the front room and using a lighter the smoke pellet will be ignited. Then the external door will be closed and the smoke will be allowed to fill the house for three minutes and only after three minutes all the doors and windows will be opened. The aim of this experiment is to understand the time required for the smoke to escape. The second test was done on PPV from the front. Here also, the front and back door of the model house will be closed and the internal door of opening to back room from front room will be kept open. The external doors will be closed once smoke pellet is ignited by keeping in the metal tray in the room. The smoke will be allowed to fill the room in three minutes and the fan should be positioned 10 cm from the front door. The experiment will be conducted three times using the three differently specified fans. The position of the fan will be same in these set of experiments. The fan will be switched on after three minutes, the time taken for the smoke to fill the room and the switching of fan will take place after the rear and front door is kept open. The aim of this experiment is to understand the time taken for the smoke to leave the room. The third experiment is done from the rear side and it is again PPV. The external doors like the front door and rear door are kept closed and the internal door is kept open. The smoke pellet which is kept in the front room is ignited and the external door is closed and the smoke is allowed to be filled the room in three minutes. The position of the fan is kept at 10 cm from the rear door and after three minutes the front and rear doors are opened and the fan is switched open. The aim of the experiment is to know the time needed for the smoke to be cleared. The second and third experiment is repeated with large fan with red covering and the fan positioned at 20 cm from both front door and rear door. Results The discussion is done about the second test when fan was placed at 10 cm from the front door. There were difference in the flow of fan based on the size and it has been found that more than 50% change difference is there in the flow of the fan between the large fan and small fan. The second fan and third fan had the same diameter and there was difference in the velocity rate. The results are shown in detailed in the table 1. Table 1. Position of the fan is kept at 10 cm from front door Fan with diameter and velocity Time taken to clear the smoke Small fan(60,1.91 m/s) Large fan(75,2.03 m/s) Large fan with red covering(75,2.61 m/s) The experiment was once again repeated using the large fan with red covering at increased distance from 20 cm.The result was that an increase of distance of 10 cm increased the flow of smoke and that bought the time down from the first experiment done at 10 cm.The data are shown in table 2. Table 2. Comparative figure of large fan with red covering placed at two different positions Time required to throw smoke out Position of the fan placed at 10 cm Position of the fan placed at 20 cm Conclusions The large fan flow rate/velocity and large diameter are needed for the effectiveness of PPV. The position of the fan is also important as the greater the distance has shown a less amount of time required to eliminate the smoke. More study should be required to know whether the increase in distance beyond 20 cm will be beneficial or not. Assumptions The door height of both front door and rear door are same and the ceiling height of both the front room and back room are same. There were no furniture as shown in the figure one. The fan is properly placed for the research as improperly placed fans can impact the result. The fans were kept in straight position as the figures will vary for tilted position.( Mittendorf, 1996) Reference Mittendorf, 1996,' Strip Ventilation Tactics', Fire Engineering, vol 149(3), pp 48. Rimen ,2000,' Use of Positive Pressure Ventilation in Fire-Fighting Operations', Fire Engineers Journal, vol. 60(206) , pp. 7–13 Svensson, S.,2001,' Experimental Study of Fire Ventilation Actions During Fire Fighting Operations', Fire Technology, vol. 37(1),pp.150-175. P.S. Ziesler, 1994,' Advances in Positive Pressure Ventilation', Fire Technology, vol. 30, pp. 269 Read More