| DANA O. PORTER, P.E. WVU Extension Service Agricultural Engineering Specialist October 1998 As cold weather approaches, this is a good time to consider ventilation needs in livestock and poultry housing. Purposes of Ventilation A ventilation system for a poultry or livestock shelter accomplishes one or more of the following (ASAE, 1993): 1. provides desired amount of fresh air, without drafts, to all parts of the shelter; The objective in ventilation of an animal shelter is to maintain a healthy environment for animals and workers in the facility. Excessive dusts, odors, and harmful gases may threaten health and safety of animals and humans. Temperature extremes reduce animal and worker productivity. Excessive moisture and corrosive gases and/or fumes can promote deterioration of building materials. Ventilation Rates Ventilation rates are designed to balance sensible heat (dry heat) gains and losses, as well as latent heat (moisture) gains and losses. Sources of sensible heat gain in poultry and livestock shelters include animal sensible heat (body heat); mechanical heat from lights, motors, etc.; supplemental heat from furnaces or lamps; and solar heat gain. Sensible heat losses include heat removed with ventilating air; building heat losses through doors, walls, etc.; and sensible heat used to evaporate water. Sources of latent heat gain are water vapor from animals (respiration and waste); water vapor from surface water evaporation (wash water, flush water, spilled water, etc.); and water vapor in incoming air. Latent heat is removed through ventilation. Additionally, ventilation should provide sufficient air exchange to provide clean air for animals and remove potentially harmful gases. Some potentially harmful gases which may accumulate in some shelters and manure storages include ammonia (an irritant which may contribute to animal respiratory problems); methane (which is highly flammable and presents an explosion hazard); hydrogen sulfide (a toxic gas); and carbon dioxide (which may cause oxygen deficiency). These gases, as well as other harmful gases and dusts, should be removed in order to maintain a healthy environment for animals and workers. Design of ventilation systems is based upon four major considerations: 1. Hot weather conditions: Under hot weather conditions, ventilation
requirements are high. Sensible heat balance is likely to be the determining factor in
ventilation design. Ventilation Methods Ventilation of structures can be accomplished naturally, mechanically, or through a combination. Natural ventilation systems move air through adjustable and fixed openings (vents, windows, doors, eave and ridge slots, etc.). Natural ventilation is usually more economical than mechanical systems for mature animals (MWPS, 1989). Mechanical ventilation systems include fans, controls, and air inlets and/or outlets. Mechanical ventilation systems include positive pressure, neutral pressure, and exhaust systems. They offer more control over room temperature and air movement than natural ventilation systems. Emergency manual control, backup power generation, and/or alarms are necessary to provide ventilation in the event of power failure. Failure of a ventilation system can result in death by asphyxiation (from lack of oxygen and increased carbon dioxide), by heat prostration, by poisoning from harmful gases, or from a combination of these (MWPS, 1990). Insufficient ventilation capacity can be detrimental to animal health and performance. In the interest of worker safety, animal safety and welfare, and business profitability, operators of poultry and livestock facilities are well advised to evaluate the ventilation capacities in their buildings. Are systems properly designed? If a building has been converted from a different use, is the ventilation system adequate for the current building use? If structural additions have been made on the building, has the ventilation system been updated also? Have new structures been added on site that may interfere with ventilation air flow in older buildings? Is ventilation system equipment well maintained? An appropriately sized, well designed, properly operating ventilation system is essential in any enclosed shelter. Sources of information For more information about ventilation of poultry and livestock shelters, you may contact the Cooperative Extension Service and the following references. ASAE. 1993. ASAE EP282.2. Design Values for Emergency Ventilation and Care of Livestock and Poultry. In: ASAE Standards 1993. American Society of Agricultural Engineers, St. Joseph, Michigan. ASAE. 1993. ASAE EP270.5 Design of Ventilation Systems for Poultry and Livestock Shelters. In: ASAE Standards 1993. American Society of Agricultural Engineers, St. Joseph, Michigan. MWPS. 1990. Heating, Cooling and Tempering Air for Livestock Housing. MWPS-34. Midwest Plan Service, Iowa State University, Ames, Iowa 50011. (List price $6.) MWPS. 1990. Mechanical Ventilation Systems for Livestock Housing. MWPS-32. Midwest Plan Service, Iowa State University, Ames, Iowa 50011. (List price $6.) MWPS. 1989. Natural Ventilation Systems for Livestock Housing. MWPS-33. Midwest Plan Service, Iowa State University, Ames, Iowa 50011. (List price $5.) MWPS. 1983. Structures and Environment Handbook. MWPS-1. Midwest Plan Service, Iowa State University, Ames, Iowa 50011. (List price $25.) MWPS. 1983. Swine Housing and Equipment Handbook. MWPS-8. Midwest Plan Service, Iowa State University, Ames, Iowa 50011. (List price $8.) Midwest Plan Service materials may be ordered from: 122 Davidson Hall Web site: http://www.eng.iastate.edu/coe/abe/mwps/pubs/index/bookind.html These materials can also be obtained from WVU Extension Service. |
