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Report, 2008

Nödventilation och larm i djurstallar

Nimmermark, Sven; Gustafsson, Gösta; Nilsson, Tania


Ventilation breakdown and narrow escapes occur at regular intervals, and sometimes these result in lethal outcomes. A ventilation breakdown in animal houses can cause a very rapid increase in air temperature, humidity and carbon dioxide concentrations inside the barn. The most severe narrow escapes occur in calf sheds (calves / beef), and houses for pigs and poultry. The most common cause of ventilation breakdown is power failure. Other causes can be failing control equipment and damaged fans. Ventilation breakdowns are most severe during summer time. According to a Swedish standard (SIS, 1992), the air temperature inside an animal house shall not exceed the outside air temperature with more than 4 ºC when it is 21 ºC outside. A limited increase of the temperature within a barn can cause a decrease in production. When the temperature exceeds an upper critical temperature a severe increase of the body temperature of the animals occur resulting in a lethal outcome. Heat stress in cows result in decreased milk production and a decrease in fertility. Hyperthermia is a common cause of death for poultry. Power failures in broiler houses are meant to be especially fatal. Pigs are meant to be especially sensitive to high temperatures since they not sweat, and not pant especially good. In directions from the Swedish Animal welfare Agency (DFS 2007:5) demands are present concerning emergency ventilation, and calf sheds (calves / beef), pig and poultry houses must be equipped with alarm equipment for excess temperature, power failure and failure concerning the alarm equipment etc. For making a summary of different brands and different models of alarm equipment available, information and pamphlets were collected from different companies. A number of equipments on the Swedish market fulfil relevant demands on alarm equipment for animal houses. A questionnaire was sent to producers with poultry, pigs and cattle in order to map the present state of alarm and emergency ventilation at Swedish farms. Totally 180 questionnaires were sent to farmers with poultry, pigs and cattle and the response rate was 72 %. The study showed that at the present time some types of alarms were missing in a number of barns. Presence of alarm was most frequent in poultry houses. Alarm for excess temperature and power failure were present in most houses with poultry. About two thirds of the poultry producers noted that they had alarm warning for alarm equipment failure. Among the pig producers about 30 % noted that they had alarm warning for excess temperature in the barn and about 20% noted that they had alarm warning for power failure and stopped fans. For producers with cattle only a small fraction noted that alarm equipments were installed in the barns. Different systems for making responsible personnel aware of an alarm exist. Combinations of different methods were frequently used. Many producers have combinations of sound / light signals, alarms to the dwellings, and alarms to mobile phones, and some producers also have alarm going further on to a central alarm station e.g. SOS Alarm or Falk. Most of the producers (more than 80 %) noted that they tested the alarm with regularity. On farms with milk production and cattle, the emergency ventilation was achieved in far most cases by the help of manually opened doors and windows, and by the help of manually 10 started electric works connected to a tractor. On farms with poultry production the emergency ventilation was managed by the help of automatic systems to a great extent. On farms with pig production, emergency ventilation was managed to a great extent by the help of windows, doors and manually started electric works connected to tractors. The study showed that power failures occurred 1-5 times per year or more frequent at more than 90 % of 120 producers answering to the question. At none of the farms animals had died as a consequence of the power failures. About 70 % of those who answered noted that they had a plan for how the emergency ventilation should be organised in case of power failure. A number of measures can be taken to improve the systems. Some producer pointed out the problem with false alarms and automatic opening of inlets / outlets leading to unwanted low temperatures in the barn during winter time. Another producer mentioned problems with the ordinary telephone net during thunderstorms and suggested switching over to mobile phones. At some farms a number of persons were meant to be able to handle problems coming up. Natural air exchange with closed and to some extent open inlets / outlets (ventilation openings) were measured in five buildings without animals by the use of trace gas technology. Measurements were made during summer time since the driving force for natural ventilation is low due to small temperature differences during that time of the year. The air exchange rate was measured by the help of sulphur hexafluoride (SF6) spread inside the buildings. The air exchange rate was calculated from the rate of concentration change by time after stopping the supply of gas. Gas concentration was registered by the help of an infrared spectrophotometer. Measurements in conventional buildings showed ventilation rates far below minimum ventilation rates. In such buildings a considerable increase of the inside air temperature will take place if animals producing heat are present. Studies in a comparatively less airtight and not insulated building showed air exchange rates well above minimum ventilation rates. The ventilation rate increased by increased inlet area and increased wind velocity. In order to estimate the rate of change in temperature during a ventilation breakdown a simple calculation model was derived from building characteristics and animal heat production equations. Calculations were made for ventilation rates of 2 m3·h-1·m-2 and 8 m3·h-1·m-2 for barns housing different animals. Calculations show a considerable increase of temperature during the first 30 minutes after a ventilation breakdown. The increase in temperature is higher in a light building compared to a heavy building. The increase in temperature are also high in buildings with pigs weighing 90 kg and houses with almost finished broilers compared to barns with cows and houses with 15 laying hens per m2 floor area. High temperatures during a ventilation breakdown can occur also at temperatures as low as 5 °C. In systems with much stored manure inside the buildings there is a risk for extremely high gas concentrations during a ventilation breakdown due to gases released from the manure. In calf sheds (beef barns) with tied animals an increase of temperature comparable to barns with dairy cows can be expected. When calves (beef) are housed on deep litter high gas concentrations may occur during a ventilation breakdown due to gases released from the litter. The studies point out that a very fast increase in temperature can occur at a ventilationbreakdown when openings between the barn and the outside air are small (inlet- /outlet openings). Calculations suggest that the temperature during unfavourable circumstances may increase up to 10 °C during less than 30 minutes. Thus, the time for arranging emergency ventilation may be very short


djurstall; ventilation; värmebalans

Published in

Landskap, trädgård, jordbruk : rapportserie
2008, number: 2008:5
ISBN: 978-91-85911-50-9
Publisher: Fakulteten för landskapsplanering, trädgårds- och jordbruksvetenskap, Sveriges lantbruksuniversitet

      SLU Authors

    • Nimmermark, Sven

      • Department of Rural Buildings and Animal Husbandry [LBT], Swedish University of Agricultural Sciences
      • Gustafsson, Gösta

        • Department of Rural Buildings and Animal Husbandry [LBT], Swedish University of Agricultural Sciences

      UKÄ Subject classification

      Veterinary Science
      Animal and Dairy Science

      Permanent link to this page (URI)