British Standards Relevant to Agriculture

British Standard Summaries

BS5502: Part 52: 1991
Building and Structures for Agriculture
Code of Practice for Design of Alarm Systems & Emergency Ventilation for Livestock Housing

The text herein is not a a full reproduction of the British Standard. It is summary based upon interpretation of the original text and not intended as a replacement for the full text. It should be used for general guidance only.

BS5502 is sub-divided into a number of individual standards. These can be broadly broken down as follows:

  • Part 0: Introduction
  • Parts 10 - 19: Reference information
  • Parts 20 - 39: General designs
  • Parts 40 - 59: Livestock buildings
  • Parts 60 - 79: Crop buildings
  • Parts 80 - 99: Ancillary buildings

This Standard gives recommendations for the design and selection of alarm systems and emergency ventilation equipment for the housing of livestock, in particular calves, pigs, poultry and rabbits when housed under intensive conditions. The recommendations of the Code are an important aide to ensuring the welfare of livestock in the event of a failure of the ventilation system.


The selection of an appropriate alarm system will depend on the class of stock housed, the type of housing employed, and the chosen type of ventilation system.

An alarm system that will warn of failure of any essential automatic ventilation equipment should be fitted in all cases where livestock are housed. To monitor failure of such equipment an alarm system should:

  • respond to temperatures which are above and, in the case of young stock, below pre-set limits; and
  • respond to a loss of electrical power.

The alarm system should comprise of the following:

  • a sensing device;
  • a means of warning the stockperson of the fault;
  • a back-up power supply from batteries to operate in the event of a mains failure;
  • facilities for regularly checking that the system is operational; and
  • instructions for operating, testing and maintaining the system.

All alarm and control units should be equipped with indicator lights which show that they are operational and should be checked daily. To reduce the risk of nuisance alarms, due to short interruptions in the power supply, a built-up delay should be incorporated.

Modes of operation

Different alarm systems will follow slightly differing automatic actions in the event of an emergency. Possible automatic actions are as follows:

  • an audible or visible alarm occurs, normally a short time after the emergency is detected;
  • an alarm and emergency action occurs after a pre-set delay; or
  • similar to the previous action, except that the system may be part of, but operate independently from, a more complex control system which may also control other factors.

Components of alarm systems: temperature sensors

An electromechanical thermostat or an electronic detector such as a thermistor is recommended. Single or multiple sensors may be used. A sensor that can be locked at its set level is preferred. The sensor and the necessary wiring should be robust and protected from damage by livestock and vermin. Some protection against excessive accumulation of dust should also be provided.

The sensor should be sited so that it is exposed to a representative sample of the air temperature in the building and is inaccessible to unauthorised persons. The sensor should also be protected from extraneous radiation sources such as heating elements or the sun. The sensor should not be enclosed such that its response time becomes slower. This means that great care should be taken in siting the sensor.

Electrical mains failure detector

Farms with multiple livestock houses should install mains failure detection devices for each house. Short interruptions to the electricity supply have no effect on temperature stability within a building, this means that all power failure detectors should incorporate a delay period to prevent nuisance alarms. This period should be a minimum of 1 minute and no more than 5 minutes. It is recommended that the delay be set at the minimum level for very young stock, for animals affected by disease or other conditions where a rapid response from the stockperson could be vital.

If a stand by generator is set to start automatically as a back-up for mains electricity failures an alarm should be given so that the stockperson can check the equipment is functioning properly.

Alarm warning device

The alarm warning device should consist of a buzzer, bell, siren and/or flashing light situated on the site. These may be associated with a personal radio pager or telephone autodial system. The warning device should be situated where it gives the maximum opportunity for immediate response.

To facilitate location of a fault on a farm with multiple livestock houses, it is recommended that a flashing light, wired to flash in the event of an emergency, is fitted to each house. A normally lit indicator light which is extinguished during a fault is also acceptable.

Information on the type of warning signal given should be made available to the stockperson.

Emergency ventilation

Whether the installed ventilation system is powered or automatically controlled natural ventilation (ACNV), it should be adequate for the stock housed but provisions should also be made to ensure that all animals receive sufficient fresh air in an emergency. The provision of emergency ventilation can only be by natural means during a failure of powered ventilation systems and may require additional openings in the building. All buildings where powered ventilation systems are installed should have extra emergency openings which can be operated if the powered ventilation system fails.

Permanent stand-by generation plant for emergency supply

The installation of a privately owned generating plant should be in accordance with BS 5502 : Part 25. With automatic starting there should be a delay of not less than 1 minute and not more than 5 minutes after mains failure before the generator starts.

Testing and maintenance

  • If an alarm occurs and the alarm device is operational for a long time, the internal batteries, whether dry-cell or rechargeable, may discharge to a low state and be ineffective if another alarm occurs soon after. Batteries should be tested after an alarm and should be replaced at regular intervals.
  • Regular cleaning of sensors may be necessary to ensure that response times are not impaired.
  • All alarm systems should be inspected daily and tested frequently, with the interval between tests not longer than one week.
  • A record should be kept of all tests and maintenance.
  • Emergency ventilation equipment which is designed to operate automatically in alarm situations should be inspected regularly.
  • All hinges, pivots, pulleys, etc., which might cause emergency flaps to stick or jam, should be inspected at weekly intervals. A lubricant should be applied where appropriate.
  • Where a wire rope system is employed connecting a series of emergency flaps the cable route should be inspected to ensure that its operation is not obstructed in any way.
  • There should be adequate space around the emergency flaps for them to operate and the access to them for resetting should not be impeded.
  • Full scale testing, in accordance with operating instructions, of all emergency flaps, back-draught shutter mechanisms and other emergency openings should be undertaken as frequently as the husbandry system will allow, with intervals between testing being not longer than two months.

A British Standard nor this summary does not, necessarily, include all the necessary information for correct implementation of the Standard to any specific application. This is purely the responsibility of the user. Standards are updated by either amendment or revision. Users should ensure that they are using the latest version.

The full text of this Standard can be obtained from the British Standard Institution

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