Dust Management

Riding arenas, particularly indoor arenas, are plagued with dust problems. Dust causes eye and nose irritations and contributes to respiratory damage in both horse and rider. It is estimated that an idle horse inhales 16 gallons of air per minute and during strenuous exercise can inhale up to 600 gallons per minute. Minimizing the amount of dust in this air should be a primary goal in footing material choice and subsequent management. In addition to horse and handler respiratory irritation, dust coats any structure and equipment near the arena. Dust rises from the surface when a large percentage of fines break loose and fl oat into the air. Naturally, lightweight particles are more prone to suspension than heavier particles. Decrease lightweight particles in three ways:

  1. Eliminate fine particles such as silt, clay, or fine sand in the footing mixture by careful footing material selection. Even coarse materials such as sand and wood products will break down over time into many fine particles, so maintenance is critical to reduce dust. In some footing mixtures, 10 to 30 percent of these materials are deliberately added for stability and water-holding capacity but realize the implications for more diligent management for dust suppression. Generally, if more than 5 percent of material passes a 200-sieve screen, the footing material will have a tendency to be too dusty. With a high percentage of fines, the arena footing material should be partially or wholly replaced. Remove manure deposited on the arena surface before it gets mixed in. Manure will break down into fine particles, contributing to the dust problem.
  2. Moisten particles to increase their weight with simple, cheap, environmentally friendly water. With no rain occurring in indoor arenas, the facility manager must be in charge 9 of moisture control. Moisture retention and evaporation is site and season dependent, so weekly checks on moisture level are important. Materials that can hold more water will increase the time between watering events (more about watering in the next section of this bulletin).
  3. Provide an additive to bind particles together. Many arena surface additives are available. Moisture retainers can be used or the surface amended to capture and hold more moisture on a dry site. Wood chips and other organic materials retain moisture well and can be a first line of defense. Synthetic or natural (e.g., coconut) fibers can be used to intertwine with footing particles to bind the materials together. Crystals and gels, some resembling cat litter, can absorb relatively large quantities of water and then release that moisture into the surrounding footing material as it dries out. Water additives can slow evaporation, increase moisture penetration, or encourage microbes to grow on footing materials for their moisture and binding activity. Peat moss holds considerable water and, when kept constantly damp, is effective at binding a footing mixture. Once peat moss dries it no longer has binding ability and becomes loose and potentially slippery. Fully dried peat moss is hydrophobic and takes considerable effort to rewet.

Oil-based products (such as palm, coconut, mineral, and soybean oil) can weigh down or glue together fine particles–similar to the effects of water application. The first application of oil is used to coat all the footing particles to increase their weight. Subsequent annual or biennial application of oil is of much reduced quantity to coat newly formed particles that have abraded off the original footing particles. The plant- derived oils may become rancid over time. Application of used motor oil is an environmental hazard. Costing more but lasting longer, pharmaceutical-grade petroleum coatings are a good option for dust suppression and adding stability to a loose surface. Petroleum coating has characteristics similar to Vaseline™ and lasts about 10 years between applications, is UV- resistant, and will not become rancid. Wax coating is even more expensive than petroleum coating but lasts even longer for dust suppression on durable footing materials.

Salt mixed into the footing material is a common dust-suppression technique. The salt holds moisture in the footing and can draw moisture out of the air and into the footing material. The salt releases moisture slowly over time between watering events. It is added to a moist footing so it can absorb water for later release. Salt application rate is 20 to 50 pounds per 1,000 square feet of arena surface area. With watering or rainfall the salt dissolves and leaches out of the footing and needs to be replenished. Salt replenishment is necessary about every 6 months and although lower in cost for initial application, the frequent replenishments eventually make it comparable in cost to petroleum coatings that last much longer.

Calcium chloride (CaCl2) and magnesium chloride (MgCl2) are most commonly used since they are less expensive and more effective for moisture holding versus table salt sodium chloride (NaCl). The effectiveness relates to calcium chloride and magnesium chloride having three available ions for binding water molecules while sodium chloride has only two ions. Salt application as a moisture-retention additive dries out hooves, and being a salt, it is corrosive to metal such as indoor arena siding and structural sup- ports when lofted with the dust. Arena managers typically wipe salt from horse hooves, sole, and lower legs once finished using the arena. These salts are effectively and commonly used to reduce the freezing temperature of the footing material during cold weather in northern climates.

Courtesy of PennState Extension