Leaving your barn windows and doors open can help improve your horses respiratory health. | Getty ImagesAir quality inside barns plays a significant role in equine respiratory health. Horses spend hours in stalls, eating hay and standing on bedding materials that release dust and other particles. Over time, exposure to airborne irritants can contribute to airway inflammation and respiratory disease, a connection researchers continue to examine.How Dust and Stall Air Affect a Horses LungsHealthy lungs in a horse efficiently exchange gases during athletic performance. At the far reaches of the respiratory system are millions of tiny air sacs (called alveoli) where oxygen enters the bloodstream and carbon dioxide is removed. When inhaled particles accumulate in the airways, that process becomes less efficient.The opportunity for allergens in poor-quality air impacts the function of the alveoli in the horses lung, says Bob Coleman, PhD, equine extension specialist at the University of Kentucky, in Lexington. In some cases, this impact can be long-lasting and have the potential to limit air exchange.Dust, mold spores, and organic particles suspended in barn air are common culprits. Researchers have shown horses housed in stalls are exposed to significantly higher levels of respirable dust (mainly from hay and bedding) than horses living primarily outdoors. Those particles can trigger inflammation in the lower airway. Over time, chronic exposure might contribute to conditions such as equine asthma.1Exposure to pollutants in the horses environment will certainly have a negative impact on the horses respiratory tract, Coleman says.Stall Odors and Horse HealthMany barn owners rely on smell as their first warning sign of a ventilation problem. While odor alone does not serve as a measurement of air quality, it can signal elevated ammonia levels. It has been suggested that ammonia levels at 10 parts per million can impact the lung, Coleman says. Humans can detect ammonia at around 20 ppm, so when we can smell it in the barn, its time to make adjustments.Ammonia forms when bacteria break down urea in urine. The gas can irritate the respiratory tract and eyes and can worsen inflammation in horses already dealing with airway disease.Humidity can intensify this problem. Ammonia breaks down in water, meaning higher humidity allows it to linger more easily in the air, which is why stalls often smell stronger on damp days.Ventilation in Horse BarnsImproving air movement in the barn remains one of the most effective ways to protect your horses respiratory health. Horses need fresh air coming in and stale air going out year-round, Coleman says.Even in cold climates, closing barns tightly to retain heat can cause harm by trapping dust and ammonia inside. Remember horses dont mind the cold as much as we do; open the barn doors and windows. To maintain good air quality, barns should be built for regular air exchange. At least six to eight air exchanges per hour are needed to maintain good air quality, Coleman says.Proper ventilation can come from a combination of ridge vents, windows, doors, and fans. These all help continuously move contaminated air out of the building while drawing fresh air inside.Hay Dust and Equine Respiratory ProblemsFeeding practices also influence the amount of dust circulating in a barn. Researchers have established hay contains mold fragments, bacterial material, and other organic particles that become airborne along with dust when horses eat. Those particles concentrate in the horses breathing zone, increasing inhalation exposure.Scientists on a study using a wearable monitor attached near the horses nose found that soaking hay before feeding reduced exposure to airborne particulate matter by more than half.2 This reduction can be meaningful for horses sensitive to dust.When comparing forage types, researchers have shown dry hay produces significantly higher respirable dust levels than alternatives such as steamed hay or haylage.Bedding and Barn Management for Equine Respiratory HealthEveryday management choices influence air quality inside the stall. Coleman says bedding, ventilation, and cleaning frequency all impact air quality and equine respiratory health.Certain bedding materials produce less dust or ammonia than others. Wood-based bedding products often release fewer airborne irritants than straw. Peat bedding can reduce ammonia levels significantly, but Coleman notes it might create more dust problems.As for cleaning routines, removing manure and wet bedding reduces ammonia production, but the process of cleaning can temporarily increase airborne dust. When cleaning stalls it is ideal to have the horses out of the stall and the barn, Coleman says. The general activity of stall cleaning has the potential to increase dust in the air and other pollutants.Even barn maintenance tools can contribute to the problem. For example, leaf blowers used to clear an aisle can send fine dust particles into the air, where horses breathe them.Some barns use stall deodorizers to reduce odor. These products change the chemical form of ammonia so it stays in the bedding. These products work as acidifiers and change ammonia to ammonium, which is not as volatile, Coleman says. Reducing the ammonia to a form that is not in the air is why the smell is masked. These products should complement good stall management rather than replace it, he adds.Special Considerations for Horses With Respiratory DiseaseFor horses already dealing with asthma or other respiratory problems, environmental management becomes even more important. Good ventilation in the space the horse is kept is critical, Coleman says.These horses might also need low-dust bedding, dust-free forage when possible, and minimal airborne particles during feeding and cleaning; however, completely eliminating dust is nearly impossible, even if you keep your horse outdoors 24/7 with a shelter available for shade or inclement weather.Dust-free hay is a challenge because all hay will have some dust associated with it, Coleman says. Still, small changes, such as wetting or steaming hay and feeding only the amount that will be eaten immediately can help prevent mold growth and limit the horses dust exposure.Take-Home MessageGood air quality in the barn requires thoughtful management of ventilation, bedding, feeding practices, and daily cleaning routines.The bottom line is good airflow and minimal dust in the air can help, but it takes effort, says Coleman.For horse owners, odors in the barn can be an early warning system. If the air smells stale or like ammonia, its likely time to open the doors, review stall management practices, and make changes that support your horses respiratory health.References: 1 Olave CJ, Ivester KM, Coutil LL, Franco-Marmolejo J, Mukhopadhyay A, Robinson JP, Park JH. Effects of forages, dust exposure and proresolving lipids on airway inflammation in horses. Am J Vet Res. 2021;83(2):153-161. DOI: 10.2460/ajvr.21.08.01262 Ivester KM, Ni J, Couetil LL, Peters TM, Tatum M, Willems L, Park JH. A wearable realtime particulate monitor demonstrates that soaking hay reduces dust exposure. Equine Vet J. 2025;57(4):10651073. DOI: 10.1111/evj.14425.