Managing Poultry House Ventilation In Pakistan

Dr A.R ShaukatDr Arbab khurshid Ahmad

Dr Waseem Abbas

We rear poultry because ofRapid growth: Birds are genetically improved to gain maturity in short

period of time to fulfill global protein requirement.Cheapest source of protein: Improved feed conversions and modern techniques have

made it possible to reduce costs to make available low priced high nutritive quality protein in market.

Availability: Due to high rearing density and rapid growth, Higher

production are obtained per unit space as compared to other live stocks.

Poultry housingHens naturally were wild birds.Domesticated with passing time to full fill human protein

requirement.Since ages backyard poultry is part of human civilization.With rapid increase in human population, the demand for

protein increased enormously which is met by improving birds efficiency genetically.

To manage large numbers we confined them.Conventional farms were initially built with less width so

that air may cross through natural air current.Conventional houses worked a lot in moderate climatic

zones but factors like increase in disease load, noxious gases, improper control of temperature, decreased efficiency were questions to be answered.

Single answer to all these questions was Modern Environmentally controlled house.

Poultry house ventilation is necessary becauseBirds need good environment.We need more fresh air to full fill the needs due to

higher metabolic rate of birds.We need more fresh air to full fill the needs due to

higher stock densities.We want to expel excessive heat if any.We need dry litter despite high density.We want to expel noxious gases e.g. ammonia. Ventilation in a poultry house supplies fresh air that is

essential to sustain life. It also helps reduce the extremes of temperature, humidity and air contamination to tolerable limits for confined chickens

Environmental conditions in PakistanWe are dependant upon the environmental conditions i.e.

climate of the region in which farm is to be constructed.Due to the location, Pakistan Climate is temperate.

Pakistan has four seasons:

A cool, dry winter from December through February.A hot, dry spring from March through May.The summer rainy season, from June through September.The fall is a retreating monsoon period of October and

November.

The onset and duration of these seasons vary somewhat according to location.

Extreme temperatures and humidity in PakistanClimate of Pakistan has great regional variation. The difference in temperature between day and night is

immensely substantial.

The Extremely hot temperature may go up to 45°C to 50+°C in the summers.

The Extremely low temperature may comes to 0°C or even less in the winters.

Humidity ranges between 10% to 100%.

Points of concern are Extreme temperatures and Humidity.

Ventilation systemsGenerally divided into two types:

(1) Natural air flow systemNatural air currents are allowed to enter into the

house.Fit for areas where outside temperature does not

exceed 33°C.House width may be maximum around 30 feet for

this system.Conventional farms are built on this principle Not best fit for our conditions.(2) Mechanical air movement (fans).Mechanical air movement is required to ventilate a

house in all climatic conditions. This system suits our climatic conditions.

Mechanical systems use electric fans as principal components to exchange air in the building. They can be divided into two distinct types(Positive pressure and negative pressure). 

Positive pressure System:

In the positive pressure system, fans are arranged to push fresh air in to the building.

Creates air velocity which produces wind chill effect.

For rearing at higher stock densities in extreme climatic conditions this system is not very much effective.

Negative Pressure system:

In the negative pressure system, fans are arranged to expel air from the building. In doing so, they create a partial vacuum or negative pressure inside the house. The pressure difference pulls fresh air through inlets into the house.

The location, distribution and size of the fans and inlets are critical if all areas of the house are to be ventilated.

We may term this system best fit for our climatic conditions.

Negative pressure system operation in different weathersTo discuss this system in changing climatic

conditions we may mainly divide it in to;

1-Cold Weather Ventilation (Minimum ventilation)

2-Hot Weather Ventilation (Tunnel ventilation)

3-Optimum weather ventilation (Transitional ventilation)

Minimum VentilationMinimum ventilation is used to provide fresh air inside the

house during cold weather. It removes excessive moisture and minimize the heat loss.

Fans exhaust air out of the house by creating a slight negative pressure inside the house. Due to the negative pressure, fresh air is pulled into the house through some planned air inlets.

The air inlets are installed either in the ceiling or high on the house side wall. These inlets are designed to direct air across the ceiling allowing it to mix with warmer air located there and to heat up before coming into contact with the birds.

Check temperature and determine the heating necessity. Doing this will help to minimize heating costs. For large scale commercial production, you can install automatic computer controllers.

Objectives of minimum ventilationProvide fresh air containing oxygen and

exhaust ammonia, carbon dioxide and other gases.

Provide an adequate air exchange to control moisture.

Get rid of excessive heat if any.Provide an in house airflow pattern that avoid

chilling birds.Reduction in fuel cost by minimizing heat

loss.

Modern house: Tools of minimum ventilation To achieve the objectives of minimum

ventilation, certain tools are required based on scientific principles.

Most important tools are exhaust fans and air inlets(vents) and other accessories to operate fans and vents properly.

If we construct a new house we may have the knowledge that how many fans and vents may be installed in that house.

Exhaust fans

Expel air out of the building. In market there are different types of fans available with varying capacity. Normally for minimum ventilation 9000 CFM capacity fans are used but we may also use fans of any capacity.

Calculation: number of fans for a houseThough this topic belongs to tunnel ventilation but to

ensure continuity we have to discuss # of fans to be installed in a house first. Formula to calculate number of fans is as follows.

No Of Fans = Cross Section x Desired velocity CFM of one fan

(Cross section= width * height of the house) Desired velocity in our climatic conditions must be more

than length of the house to get less than 1 minute air change.

CFMs of air expelled by a single fan depends upon the size and efficiency of fan recommended by the manufacturer.

Tools of minimum ventilation Controllers: It is an electronic device that collect information from different sensors and execute scheduled tasks. Static pressure switch provide information to controller and controller operates power track to open or close vents accordingly.

Inlets(vents): fresh air is pulled into the house through vents. Vents are distributed through out the house in uniform pattern. Number of vents depends upon size of vent and 40% of total capacity of fans installed in house so that air may pass at a velocity of 700 Feet per minute .

Calculation;Number of vents for a house

Area for vents=Total no of fans x cfm of one fan x 40% 700 f.p.m

Total no of vents=total area for vents Area of one vent

(40% of total ventilation is maximum limit of minimum ventilation).

(Air should pass across the vent at a speed of 700 fpm).

We can purchase vent of any dimension from market. Greater the area of vent, Less would be the number of vents and vice versa which are supposed to be installed in house uniformly.

Tools of minimum ventilation Static pressure sensor: sensor is installed with controller to sense static pressure and give feed back to controller so that it may open or close the vent according to static pressure to avoid chilling.

Power track : it is an electrical device attached mechanically to vents and on the information of controller, Operates the vents according to the static pressure.

Minimum ventilation:Tools working sequence

Tunnel Fans : OffMin. Ventilation Fans : on

Cooling Pad : ClosedVents : Open

Evaporative Cooling : OffTunnel door : Closed

Lethal and desirable level of gases.

One of the most important objective of minimum ventilation is to remove gases in order to provide quality air to birds.

Three primary air quality variables are of utmost importance.

Carbon dioxide, Humidity, Ammonia.

Table 1. Common gas levels in poultry houses

Gas Symbol

Lethal Desirable

Carbon Dioxide

CO2 Above 30%

Below 1%

Methane CH4 Above 5%

Below 1%

Ammonia NH3 Above 500ppm

Below 40ppm

Hydrogen Sulfide

H2S Above 500ppm

Below 40ppm

Oxygen O2 Below 6%

Above 16%

How much to ventilateKnowing how much to ventilate during cold weather is

crucial but to simplify a minimum ventilation value of 0.588 cubic feet per minute per kg body weight is suggested. Ventilating too little can lead to poor air/litter quality, resulting in bird health and performance issues. Ventilating too much can lead to drafty conditions and high heating costs.

Static pressure is of importance to avoid chilling and its desired value is dependant upon width of house. As a rule of thumb the width of house in meters is equal to the static pressure required in Pascal.

Practical applicationMinimum ventilation value

Calculate total live weight in house by multiplying average weight in kilograms with number of birds present in house.

By multiplying total live wt with 0.588, we will have total cfms required to ventilate house.

Adjust the fan runtime by dividing total cfms on cfm of one fan.

Practical application of static pressure value:Lets say width of house is 45 feet.Divide 45 by 3.2808 to convert it into meters.45/3.2808 gives 13.71.So 13.71 Pascal pressure is required.Divide 13.71 by 249 to convert it into inches

of water column.So 0.055 inches of water column static

pressure is required to pull the air up to the center of house.

Example To Elaborate Minimum VentilationLet suppose we have a house of Length 500 ft, Width 45

ft, Total number of birds are 40,000 and average weight of the bird is 500 grams. Capacity of one minimum ventilation fan is 9000 CFM. Outside temperature is 2 Degree Centigrade. How to calculate its ventilation?

Calculation of minimum ventilation:

40,000 x 500= 20,000 kilograms 1000

20,000 x 0.588= 11760 CFM required

11760 = 1.30 Fans 9000

Example To Elaborate Minimum Ventilation1.30 fans mean that we may operate one fan

continuously and one fan on 30% timer. We may also operate 2 fans on 65% timer or operate 3 fans on 43% timer.

Static pressure:45 / 3.2808 = 13.71 Pascal 13.71 / 249 = 0.055 inches of water

column(1’’ of water column =249 Pascal)

Age wise recommended minimum ventilation Per Bird rates.

Some studies recommend typical minimum ventilation rates per bird depending upon the age of the broilers. This table is added specifically due to the reason that minimum ventilation at day first is a little bit tricky on body weight basis.

How to avoid chilling The critical factor for successful minimum ventilation is making sure that in coming cold air mixes uniformly with and is warmed by in house air before coming in contact with the bird. The setup that most constantly meets this requirement is a negative pressure system using side walls exhaust fans with adjustable air inlets.The partial vacuum created in the house( static pressure 0.05---0.1 inches of water column) pulls air in evenly and at the same high velocity through all inlets so that the mixing of outside and in house air is uniform through out the house.

Transitional ventilation Fall and spring are transitional seasons when difference

between day and night temperature may range from 15 to 20 degree centigrade. So this is a difficult time for farmers to manage poultry house ventilation.

Farmer must be alert to need for ventilation setup changes and manage the transition smoothly.

Transitional ventilation goal is to maintain in house optimum temperature that support best bird performance.

In transitional weathers wind chill is required at day time but may hurt bird performance at night. So keep on switching between minimum and tunnel depending upon outside temperature is necessary.

Objectives of Transitional ventilationTransitional ventilation fills gap between hot

weather and cold weather ventilation needs. Maintaining in house temperature that support

best bird performance during changing weathers.

Switching between minimum ventilation and tunnel ventilation to get wind chill when required in any part of day and stopping when required.

Switching between side wall fans and tunnel fans as required.

Tools of transitional ventilation Side wall fans Tunnel fansInlets/ventsStatic pressure switchTemperature sensorsControllersPower trackTunnel doorsTunnel air inlets

Transitional ventilation:Tools working sequence

Tunnel Fans : Occasionally OnMin. Ventilation Fans : On

Cooling Pad : Occasionally OpenVents : Occasionally OpenEvaporative Cooling : Off

Tunnel door : Occasionally Open

Optimum temperature requirement of broiler as grow out progresses

•Our goal in ventilation is to keep in house temperature at right levels.

•The chart shows the daily temperatures that produce the best broiler feed conversion as a grow out progresses.

Age In days

Temp in centigrade

1 333 325 31.57 319 3013 2817 2721 2625 2429 2233 2235 2239 2242 22

Tunnel ventilationFor keeping the birds cool during hot weather, we use

tunnel ventilation. Tunnel ventilation system in the broiler house consists

of large air inlets at one end and fans at the opposite end. The fans used in one end pull air the length of the house at a velocity of 500 ft per minute or more.

This system removes excessive heat from the building very fast and make a wind chill that provides the birds additional cooling.

Evaporative cooling system is also used for cooling the house, when tunnel ventilation system alone is not sufficient enough.

Tunnel ventilation Objectives

Main goal of Tunnel ventilation is cooling birds.

Maintain end to end temperature difference as low as possible.

Maintaining low humidity during extreme hot and humid weather.

Get rid of immense heat dissipated by the birds.

To obtain wind chill effect as per requirement of the birds.

Tunnel ventilation:Tools working sequence

Tunnel Fans : OnMin. Ventilation Fans : off

Cooling Pad : OpenVents : Closed

Evaporative Cooling : OnTunnel door : Open

Principles of tunnel ventilation Pulling air in a single direction from one end to the

other end produces a certain velocity. This air movement from one end to the other carries all the excessive heat dissipated by the birds and excessive humidity, gasses outside the house.

With increasing air velocity effective temperature felt by the bird is decreased.

Evaporative cooling system decreases the temperature by adding humidity in the house. It is very important to realize that the evaporative cooling produces far less cooling than does the air speed.

Points to be considered in tunnel ventilation Ventilate with Tunnel, only when cooling the

birds is the goal.Turn on the right number of fans for cooling

needed, depending upon the age of the birds.Watch the birds not only thermometer to see

how much cooling is needed.Do not run fewer than half of the installed tunnel

fans if you intended to be tunnel ventilating .Monitor and maintain adequate air flow.If running evaporative pad cooling static

pressure should be 0.05 to 0.1 inches of water column.

Tools of tunnel ventilation Exhaust fans:Expel air out of the building and combination produces velocity of air in the house. Number of fans are determined through cross section of the house and desired velocity.No of fans = Cross Section x Desired Velocity

CFM of one fan

Tools of tunnel ventilation Cooling pads: it is a pad

made up of cellulose with different flute angles. When we pour water upon pads and air pass through the wet flutes, air cools down due to addition of humidity. That cooled air is pulled in a single direction by exhausts fans through out the house.

Air velocity across the pad must be 350fpm with operation of all fans.

Number of Cooling Pads in a Modern HouseWhen we have desired # of fans what may be the pad area to support these fans properly in extreme hot weather.

Area of cooling Pad= Total no of fans x CFM of one fan 350 fpm

Total No of pads=total area for pads Area of one pad

(Air should pass across the cooling pad at a speed of 350 fpm).

Number of pads may be determined by dividing total area required by area of 1 pad.

Tools of Tunnel ventilation •Tunnel door•Cooling pads motor•Power track for the operation of tunnel door•Controller •Temperature sensors•Humidity sensor •Humidity switch

Ventilation during hot and dry weatherWith increase in temperature a poultry house

needs higher ventilation. With increasing age and temperature we may

keep on operating more fans until we reach to a velocity of 1 minute air change.

If the effective temperature felt by the bird is still high then we have to operate cooling pads.

When the air passes through the wet cooling pads it is cooled down in dry weather and directed towards the ceiling of the house to avoid chilling of the birds at pads area.

Ventilation during hot and dry weatherThe cooled air would be transported to

the end of the house in 1 minute. So the temperature of the house would

come down quickly and it would be sensed by the sensors and conveyed to the controller. The controller would bring down the air velocity by shutting off fans to avoid chilling by combined effect of low temperature and wind chill.

End to end temperature difference

•In tunnel ventilation end to end temperature difference must be as low as possible.•Higher the air velocity lower would be the end to end difference.•In the given diagram the end to end difference is almost 2 degree with an air velocity of 550 fpm.•it also depends upon insulation of the house.•Poor the insulation higher would be the end to end difference.

Ventilation during hot and humid weatherThis is the most challenging weather in Pakistan for

poultry farmers.As we approaches the month of July in Pakistan

there is a sudden increase in the relative humidity outside due to Moon Soon.

In this weather our tool of minimizing house temperature through evaporative cooling does not work properly due to increased humidity.

We are supposed to increase the air velocity as much a possible in this type of condition.

Ventilation during hot and humid weatherBut still despite achieving the maximum possible

air velocity, we do need to decrease the temperature by a certain degree due to the fact the temperature goes beyond 35 degree centigrade.

In such conditions we operate pads on timer basis.

Off time of the pad is calculated by observing the time in which the pad is dried off and the on time is determined on the basis of observation that in how much time the pads become completely wet.

Increasing air velocity to 40 seconds air change or less may give good results.

Thank YouFor

Attention.