referring to fig1 a poultry house having means for maintaining a relatively constant internal pressure relative to fluctuations in the ambient outside air pressure is shown . the poultry house ( 1 ) has a plurality of fans ( 2 ) which are part of the air ventilation system . a plurality of vent openings ( 3 ) are distributed about the building , for the discharge of exhaust air therethrough . a pressure sensor ( 4 ) is locate outside the building for reference . a second pressure sensor ( 5 ) is placed in an interior of the building and is connected to a pressure transmitter ( 6 ) that outputs a pressure signal to a controller ( 7 ). the controller ( 7 ) receives the pressure signal and then compares it to a preselected set constant pressure , typically determined by an operator . the set pressure should be slightly above a typical range of ambient atmospheric pressure variations , as this is the easiest scenario for achieving a constant internal pressure . the range could be from about 30 . 0 to about 3 . 1 . 0 with about 30 . 5 preferred . relatively constant internal pressure means that the pressure is close to the set point approximately 75 % of the time or more . fluctuations are inevitable when doors open or other events occur , though the system should be designed with sufficient capacity to limit the excursions in time as well as in the degree of difference from the set point . generally , a fluctuation of about +/− 0 . 2 inches of water is acceptable . the controller calculates the difference between the set pressure and the actual internal pressure and determines whether the internal pressure is too high or too low . from this determination , the controller sends a control signal for adjusting the pressure in the poultry house . in one embodiment of the invention , this involves opening the dampers to decrease internal pressure ( letting more air out of the building ) or closing the dampers ( keeping more air in the building ) to increase pressure . to the extent possible , a relatively constant positive pressure should be maintained . alternately , the fan speed control could be adjusted to increase or decrease the amount of air supplied to the building , with a corresponding increase or decrease in internal pressure . in a preferred embodiment of the invention , one or more of the fans are reversible and therefore can be used to either supply air into the building or be used as exhaust fans . in this way , not only can the pressure in the building be controlled , but adequate ventilation through the building assured . in addition , by altering which fans blow into the building and those which blow out , changes can be made to accommodate differences in the season . for example , during colder weather , air could be supplied through the fans at a top of the building so that there is some mixing with the warmer internal air near the roof to temper the cold air before it reaches the poultry . during warmer weather , the higher elevation fans are used as exhaust fans to assure that the hottest air is removed from the building . efficient ventilation and temperature control can then be achieved , as well as an increase in egg production . by simply having more fans supplying air than the number removing air , the positive pressure can be obtained , and for additional control , dampers can be utilized in combination with the fans to assure both that the positive pressure is maintained and that adequate ventilation is assured . referring to fig1 a building 1 has poultry housing portion 2 accessible through first and second double entry doors , 3 and 4 , respectively with a space 5 therebetween . this forms an air - lock to limit the loss in positive pressure as doors are opened by operators , etc . this also assists in climate control , preventing a rush of cold or hot air into the building as one set of doors usually closes before the other doors open . cooling and heating can be provided by any conventional means such as using earth tubes for cooling , or propane heaters for heating , and the invention is not limited by the choice of temperature control system . the building 1 has another entry 6 leading to a packing area 7 , with an egg cooler 8 . doors 9 lead to a shipping / receiving area 10 and doors 11 exit the building , the series of doors providing an air - lock for pressure maintenance . the building 1 has a plurality of fans 12 distributed about the building , as well as a plurality of actuated damper openings 13 which work in a coordinated effort to maintain a relatively constant internal air pressure as will be described below . referring to fig2 a block diagram of the control scheme is shown indicating the elements usable for controlling the interior pressure of a poultry house . a pressure controller 14 receives a signal from a pressure transmitter 15 and a sensor 16 located within the building 2 . one or more sensors and transmitters may be used . the pressure controller may optionally receive a signal from an outside pressure sensor 17 and pressure transmitter 18 . this can be used by an operator for reference , and it may be useful to record the outside pressure relative to the inside pressure to confirm that the pressure within the poultry house is relatively constant compared to the outside pressure . if not , this may indicate that a door is open or that there is some other problem with the system that should be checked by the operator . this may also be used to review egg production relative to building pressure over a given time period . the pressure controller is given a set point 19 by the operator , that is , the target pressure to maintain in the building . the pressure controller then compares the set point to the actual internal pressure and issues a control signal that may be sent to a damper adjusting device 20 which controls a damper actuator 21 , and / or a fan direction controller 22 and / or a fan speed adjustment device 23 which control the fan motors 24 . any one or a combination of these may be used to change the internal pressure to bring it closer to the set pressure . again , opening the damper reduces the pressure , closing the damper increases the pressure , etc . another option is to selectively turn on or off various fans , though this does not provide very fine pressure control . preferably , pressure is controlled by adjusting the damper openings , as this is the easiest and cheapest way to implement the system , and cost is a concern in egg production . referring to fig3 a , an existing type of poultry house 25 is shown which can be retrofitted for utilizing the present invention . in this embodiment , the air lock type of double doors are not included , but these could optionally be added . the first step in the retrofitting is to reverse some of the plurality of fans either physically or via control means so that some fans blow air into the structure as opposed to all the fans withdrawing air from the structure . a pressure sensor and transmitter 26 are mounted in the building and connected to a controller 27 , which as described previously is used to maintain a relatively constant internal pressure . as shown in fig3 b , the fans 28 and 29 blow air into the building while a fan 30 and dampers 31 allow air to exit the building . thus , several fans continue to be used as exhaust fans , and the existing dampers are used but have actuators 32 responsive to control signals which assure that a relatively constant pressure is maintained as opposed to the negative pressure utilized in the prior art . an a outside pressure sensor / transmitter 33 provides a reference signal to the controller . by maintaining a relatively constant internal air pressure , it is believed that egg production can be increased by about 2 - 5 %. while it is not completely understood as to why the control of air pressure promotes egg production , it is believed that the variations in atmospheric pressure may disturb the poultry while a constant slightly positive pressure may have a calming effect on the poultry . it is known that a calming effect can result in an increase in egg production . utilizing the present invention thus promotes and increases the yield in egg production while at the same time providing additional opportunities for better control of the environment in a poultry house . even when utilizing a positive building pressure , the poultry house is assured of receiving adequate intake of fresh air so as to prevent a buildup of heat , moisture and fumes which could have a detrimental impact on egg production . while preferred embodiments of the present invention have been shown and described , it will be understood by those skilled in the art that various changes or modifications could be made without varying from the scope of the present invention .
a method and apparatus are used to maintain a relatively constant , preferably positive , pressure in a poultry house which houses egg laying poultry , the constant pressure resulting in an increase in egg production while assuring adequate ventilation in the building .