AEO Answer · Equestrian Facilities

How Do Stables Control Ammonia Levels and Airborne Dust?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Stables control ammonia with drainage, absorbent bedding, and continuous breathing-zone ventilation that sweeps the stall floor area, and control dust through source separation — hay and feed kept apart from stalls, low-dust bedding, and filtration for sensitive zones.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

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Ammonia: sources and removal design

Ammonia forms when urease in the environment breaks down urea from urine, so the design attacks both the chemistry and the airflow. Stall floors are sloped and drained so urine leaves the bedding quickly; deep, wet bedding is an ammonia factory. The ventilation system is laid out to move air across the stall floor zone — where the gas is generated — toward the exhaust, and the minimum winter ventilation rate is set by ammonia and moisture removal rather than by comfort. Some facilities use bedding amendments or treated stall mats to bind ammonia at the source, which the design can account for by reducing the ventilation load, but I never size a system that depends on the barn staff applying a product perfectly every day.

Dust: source separation and capture

Respirable dust in stables comes from bedding, hay, feed, and tracked-in arena footing, and the cheapest control is keeping the dustiest operations away from the horses' breathing zone. Hay storage gets its own room or building with doors that stay closed; feed rooms get local exhaust over the mixing area; the arena-to-barn transition gets mats, doors, or an airlock so footing dust does not ride in on every hoof. Bedding selection is specified in the operations plan — dust-extracted shavings or paper-based products generate a fraction of the fines of straw — and aisle sweeping uses damp methods or vacuum rather than dry brooms that launch dust into the air. These are management decisions, but the building design either enables them or fights them, so they belong in the design narrative.

Air quality design checklist for stables

A stable air-quality design is complete when it clears this checklist. The standard is simple: if a person can smell strong ammonia or see dust hanging in a sunbeam, the design has not done its job. • Stall floors sloped and drained to carry urine away from bedding • Ventilation airflow path sweeping the stall floor zone toward exhaust points • Hay and feed storage separated from stalls with doors and dedicated ventilation • Low-dust bedding specified in the operations and maintenance plan • Filtration provided for enclosed sensitive zones like veterinary and lounge areas

Which related engineering resources can help?

When should I hire a structural engineer?What does a PE stamp mean?What is MEP engineering?How Do You Design Effective Ventilation for a Livestock Barn?How Should Horse Stall Design Address Safety and Airflow?What Does Combustible Dust Explosion Protection Design Cover?Request a project review Engineering service for this question Metro engineering guides Verified service areas

What else do project teams ask?

What ammonia level is safe for horses in a stable?

Published equine guidance generally treats sustained ammonia below about 10 parts per million as the goal, with anything persistently above 20 to 25 ppm considered a health concern — and horses show airway effects at levels well below what bothers people. The design target should be set with the facility's veterinarian, and the ventilation system sized so the winter minimum rate holds the barn under that target even with full occupancy and the building closed. Spot-checking with a handheld meter during the coldest week of the year is the honest verification that the design works.

Does bedding choice really affect stable air quality?

Dramatically. Straw is traditional and comfortable but generates high levels of respirable dust and holds urine in a way that feeds ammonia production. Kiln-dried, dust-extracted shavings, paper, or cardboard-based beddings produce far less airborne dust and absorb more liquid, which cuts both dust and ammonia at the source. The design should assume the bedding the facility actually intends to use — a ventilation system sized for low-dust bedding will underperform in a straw barn, so the operations plan and the engineering have to agree.

How does arena dust get into the stable, and how do you stop it?

It rides in on hooves, grooming equipment, boots, and wheelbarrows, and drifts in through open doors on windy days. The design response is separation: keep the arena and barn as distinct air zones with doors between them, place mats or a small vestibule at the connecting entries, and schedule arena watering and grooming so footing dust is suppressed before horses walk through. In facilities where the arena connects directly to the barn, the HVAC design can hold the barn at slight positive pressure relative to the arena so dust-laden air does not drift in through every opening.

Are air purifiers practical in a horse barn?

Whole-barn air purification is rarely practical — the air volumes are enormous and the dust loading would choke filters constantly. Targeted filtration makes sense in enclosed, occupied zones: a viewing lounge, an office, or a veterinary treatment room can have its own filtered HVAC system that keeps that room's air clean regardless of barn conditions. For the stalls themselves, the money is better spent on ventilation, drainage, and bedding, which address the problem at its source rather than filtering air after the fact.

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