Emergencies on Livestock Farms (PB1147)

Alarms and Emergency Ventilation Systems

6 Where livestock depend on an automatic ventilation system, it is now a legal requirement to have both an alarm system and an alternative emergency ventilation system. The Welfare of Livestock Regulations require that: farm_emergencies_fig1.gif(25215 bytes)
  • when livestock are dependent on an automatic ventilation system, there must be an alarm to warn of power or system failure;
  • provision must be made for an alternative means of ventilation so that failure of the automatic system will not result in unnecessary pain or unnecessary distress to the animals;
  • all equipment referred to above should be inspected by your stock keeper (or other competent person) not less than once every 7 days and any defects should be rectified immediately.
7 When something goes wrong with a ventilation system which is dependent on electric fans, it is essential to have an effective alarm. Experience has shown that the range of possible faults is considerable as are the effects on welfare, even with diligently installed systems. Example faults include:
  • an alarm only working on power failure; low voltage may fail to turn the fans sufficiently, result - mortality and loss of stock. IT IS ESSENTIAL TO HAVE THE ALARM SYSTEM MONITORING OFF LIMIT TEMPERATURES AT ALL TIMES;
  • an alarm system with a broken circuit due to rodent damage, result - mortality and lost stock;
  • an alarm system with a telephone call-out given a low priority because a generator is available - generator burned out, result - a serious threat to welfare and thousands of pounds worth of stock losses;
  • emergency ventilation panels or fail-safe stuck or nailed in following false alarms, result - death of stock due to heat stress and / or smoke inhalation during a fire.
8 All of these events can be prevented, saving thousands of animals' lives. It is for these reasons that the words, 'an effective alarm system' have been used in the 1994 Regulations and why it is very important for you to choose the alarm system carefully and have it installed by a qualified electrical engineer. It is also important to test it every 7 days.
9 Your alarm system should be installed to suit your particular circumstances. For example, there may be less need for a fast response where a failure of the primary ventilation system will not lead to immediate livestock suffering.
10 The most common welfare problem caused by ventilation failure is heat stress. The temperature at which heat stress begins is known as the upper critical temperature (UCT). The UCT depends upon a number of factors. The ventilation rate necessary to keep house temperatures below UCT depends on the outside temperature, solar radiation strength, the level of reflectiveness of the roof (and its insulation characteristics) and the stocking rate.
11 On large intensive livestock units, autostart generators are standard equipment. Like alarms they should be tested every 7 days, and items such as the fuel level and battery should be checked. However, generators only provide backup against electrical failure, not system breakdowns such as fan or control failure. For this reason as an additional precaution, convectional fail-safe systems are recommended though they are not mandatory. The size of the fail-safe suggested has been that capable of preventing the temperature lift due to stock heat exceeding 5C. This is because in general this design capacity prevents house temperatures rising above 31 - 32C. For higher temperatures design options such as good roof insulation, lower stocking density, more fan blowers and drinking facilities should be considered. This advice does not only meet welfare concerns but also meets sensible financial risk calculations.
12 The temperature lift value of 5C is not intended to be taken as exactly 5.0. In coastal and upland areas for example, 5.5 or even 6 is probably acceptable because the chances of windless weather are less. However, the converse may also be true depending on the geographical location in relation to contours and altitude. The total fail-safe area needs to take into account any adventitious leakage and so, for leaky houses, a nominally smaller fail-safe will normally do but an expert should be consulted for advice. Many livestock houses are leaky. Note that this leakage is a good thing during system failure, which should be rare, but is of course a thoroughly bad thing when we are trying to control winter temperature for reasons of feed conversion in pigs and poultry.
13 If the site is permanently staffed round the clock and the houses are small, it may be sufficient to open doors or to operate manual inlets and outlets. The Regulations do not say that emergency equipment must be automatic. In summary, unless you are sure that your manual systems are adequate, it is wise to have a fail-safe designed to a 5C lift, or to that appropriate to your situation. The areas of failsafe opening depend on the number of animals, the type of animal and the height difference between the inlets and the outlets.
14 Low temperatures may also stress animals, for example young stock, particularly if combined with damp and draughts. Therefore the designer of livestock housing needs to consider a wide range of animal welfare needs.
ADLib logo Content provided by the Agricultural Document Library
© University of Hertfordshire, 2011