One of the major problems when riding your horse in an arena is the dust, especially in indoor arenas. Dust can cause lot of problems for the rider and the horse, including increasing allergies and causing inflammation in the eyes and respiratory tract. An idle horse inhales about 16 gallons of air per minute and a horse in strenuous exercise inhales about 600 gallons of air per minute, so any dust in the air can cause a serious problem in the exercising horse's lungs.
The Penn State College of Agriculture indicates that it is important to eliminate fine particles such as silt, clay or fine sand in the top footing mixture. Even course materials such as sand and wood products can break down and become dusty over time, especially if manure is not removed frequently as it breaks down and contributes to dust. The next step to decrease dust is to add water. Deep watering is important to not only decrease dust but to also add stability for riding. The top three inches of the soil should be evenly moist and a soil moisture meter can be used to determine when further watering is needed. You can also decrease dust by using an additive to bind particles together; many of these additives available. Wood chips and other organic materials retain moisture well and may be a good first option. Synthetic or natural fibers can be used to bind materials together, and crystals and gels that resemble cat litter can absorb a large amount of water and release it as needed. Oil-based products like coconut or soybean oil can weigh down or glue together fine particles. Salt has commonly been used to suppress dust in arenas as it holds moisture and also draws moisture out of the air although salt application must be repeated usually every 6 months.