Air Quality in Horse Stables

Abstract

A large number of people are highly engaged in the equine industry around the world, especially in industrialised countries. For example, in the USA about 4.6 million Americans are directly involved in the equine industry, and in Sweden the industry provides full-time employment to over 30 000 people. Horse riding is the second biggest sport in Sweden after soccer, engaging approximately 6% of the population, and is by far the biggest sport for girls. Consequently, many people spend a considerable portion of their day in stable environments, either as workers in the care and training of horses, or in their leisure time. The type of buildings used for stabling horses can vary widely. Some are newly built and thus designed solely for housing horses, whereas others have been converted or “retrofitted” from barns used for other farming activities, such as housing cattle or for feed storage. However, regardless of design these buildings have many common requirements for indoor environment, including selection of type of feed and bedding, and the need for continual removal of faeces and urine. Moreover, the building ventilation must provide adequate exchange of fresh air to the horses’ living space to regulate the stable temperature and remove moisture, stable gases and organic debris produced by the horses and their activities. There is no need to remove excess heat in stables in the winter in northern climates. However, this puts more focus on ventilation, which must rid the stables of moisture, odour, and ammonia that have built up in the more closed environment of the stable. Moisture originates from horse’s respiration, faeces and urine, and other stable activities such as showering the animals, and general stable cleaning. Accompanying this moisture build-up is increased risk of condensation, intense odour, and increased ammonia release from bedding that ventilation must remove. How much ventilation should be provided? Ventilation of one air change per hour (ACH) means that the total volume of air in the stable is replaced in one hour. Guidelines for horse stables suggest providing between 4 to 8 air changes per hour to reduce mould spore contamination, minimize condensation, and reduce moisture, odour, and ammonia accumulation (Horse Stable Ventilation, 2003). Thus, for the mean of 6 ACH a stable’s ventilation system must be capable of a complete air change every 10 minutes. With the inevitable seasonal appearance of subzero winter weather, horse owners occasionally work against these principles of ventilation in an unheated building by trying