How to use a hand-held carbon dioxide monitor to evaluate summer ventilation in poultry houses
Minimising temperature gain, or the difference between the temperature inside and outside of a poultry house, is the first objective of any poultry ventilation system in hot weather.
Carbon dioxide measurements are a rapid method of evaluating the temperature gain and airflow in poultry houses. They are easier to conduct and appear to be less variable than direct measurements of temperature gain.
In a study of 46 commercial poultry houses in Manitoba, Canada, a strong linear relationship (r2 = 97 percent) was observed between house carbon dioxide level and temperature gain. House carbon dioxide levels under 700 ppm were associated with a temperature gain of 1.5 deg C or less. Service people and farm managers can use hand held carbon dioxide monitors to provide quick estimates of airflow and heat buildup in poultry houses.
Air temperature, carbon dioxide level and airflow were measured in 46 poultry houses (nine broiler, 26 layer, eight breeder, one pullet and two turkey houses). All measurements were taken when the stoves were turned off and the birds provided the only source of heat in the houses.
For cool weather conditions (temperature gain over 15 deg C), all measurements were done in layer houses with manure belts or gutters where the manure could be removed regularly to prevent ammonia buildup.
Outside air temperature was measured with a digital probe thermometer at the outside face of the inlet or eaves where the air first entered the house. The thermometer was positioned to keep it out of direct sunlight.
During each farm visit, outside temperature was measured on two or more occasions at each of three or more locations. The same thermometer was used to measure temperature inside the house.
Airflow through the houses was estimated based on airspeed of the fan exhaust and area of the fan opening. Fan airspeed was estimated based on nine measurements with a Kestrel vane anemometer. The method of determining fan airflow has been explained previously (Bennett, 2004).
Carbon dioxide was measured using an ACR Falcon 206 hand-held carbon dioxide meter. Temperature was measured at all locations where carbon dioxide was measured but in large layer houses, temperature was measured in more locations than carbon dioxide.
Carbon dioxide levels were relatively uniform between different locations in the poultry houses. The carbon dioxide produced by the chickens was warm and tended to rise and mix in with the general airflow in the house.
The steady increase in carbon dioxide as temperature gain increased was expected due to the low airflows needed to trap bird heat in the cool months when a large temperature gain was needed.
A reasonable objective for hot weather ventilation would be to keep carbon dioxide levels below 700 ppm.
In addition to predicting temperature gain, the carbon dioxide levels provided an estimate of airflow in the houses.
As airflow increased above the minimum winter ventilation rate (approximately 0.15 litres/s/kg of live weight), carbon dioxide levels dropped dramatically. At flow rates over 1.5 litres/s/kg, however, further drops in carbon dioxide levels were difficult to discern.
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Article made possible through the contribution of Australian Poultry Science Symposium (APSS) 2007.