If you're a horse owner and already concerned about the quality of the air in your equine establishment, you're absolutely right.

Understanding air quality is important because high levels of dust and other irritants in the air are unseen in barns and stables and very often the appropriate ventilation to combat them is simply not there.

Firstly, horses living in a dusty environment are all too susceptible to inflammatory airway disease (IAD) and research shows IAD is very common.  This can be described as follows:

• Discharge from the nose of the horse
• Wheeziness and laboured breathing
• Coughing
• Flared nostrils
• Below normal expected performance
• Unwillingness to exercise

It is important therefore for horse owners to put into place steps to minimise exposure to air irritants bearing in mind that horses and stable hands may spend as much as half a day in an enclosed environment.

Dust can accumulate in a stable from many sources and is analysed under the following forms according to size;

• Total dust – can be seen, physically cleaned away and removed for the stable.
• Dust that can be inhaled – made up of smaller particles and can penetrate the upper portion of the airways. This is called thoracic dust.
• Respirable dust able to reach further into the airways – Finer dust than thoracic dust can penetrate into deeper airways and, because of its minute size, is not caught by mucus for example. Lower airways in horses are often affected by these finer particles.
• Fine and ultrafine particles – Ultrafine dust is so small it is able to infiltrate the bloodstream and cause problems in many parts of the body. There is ongoing research into this form of dust.

Combinations of all the above forms of dust exist in all equine establishments, and it may not be realised how it is contributed to by any or all of the following sources:

• Hay, bedding and unnecessary items left in the stable
• Spores of mould exist in hay, grains, tack and equipment.
• Bacteria and particles of a virus from a sick animal can contaminate the environment
• The transfer of tack and equipment, feed buckets etc can spread the existing dust particles and disease

Ammonia is also a frequent source of concern and a contributor to poor air quality.  It is usually recognised by its smell, causing stinging and watery eyes. Test equipment is available to monitor the levels of ammonia present.

Decomposed urine in stable bedding will produce ammonia which will be an irritant to the respiratory airways.  Ammonia levels will be nearer the floor so that horses lying down or ponies and foals are exposed to higher levels of ammonia significantly.

There are 3 basic types of ventilation: infiltrated, mechanical and natural

Replacing stale air with fresh air is the process of ventilation, and most stables do not have a system of adequate ventilation, thereby increasing the risk of respiratory diseases.

Infiltrated ventilation occurs by air entering through gaps in the walls or floors and around doors and windows. This should not be relied upon as an adequate form of ventilation.

Mechanical ventilation is, as its name suggests, a form using fan equipment and a system of vents in ducts with grilles in the walls etc.

Natural ventilation is the use of a chimney or stack included in the roof construction. Wind blowing across the roof of the stable can help to improve the air quality, as well as the effect of air blowing from one side to the other.

The air exchange rate is an important measurable factor to evaluate the effectiveness of your stable ventilation.  The recommended air exchange rates vary depending on the time of year and the volume of the stable.  A 12'x12' stable with average roof height should be achieving 6 air changes every hour to be considered well ventilated.

Temperature and moisture differences between inside and outside conditions can affect the effectiveness of the stack system.  With warm temperatures outside hot air in the stable goes out through the stack, and cooler, fresh air is drawn in through windows, doors or vents.  However, in cooler temperatures, the difference between inside and outside is less and under these conditions, the stack is less effective.

Vents in eaves and ridge of the building will also improve ventilation, allowing cool, fresh air to be drawn in to replace the warm air going out through the roof.  Vents along the entire ridge length are ideal to facilitate the cycle or exchange rate.

Basic changes to stable management can help to improve air quality.

• Remove unused tack and equipment
• Choose dust-free bedding materials
• Feed Quality
• Barn doors open or closed
• Cleaning and sweeping

Remove unused tack and equipment

Try to avoid leaving equipment collecting dust in the stables.  Although this only removes the visible dust, it is a good first step to dust reduction.  The dust particles that are most harmful are those unseen by the eye.

Choose dust-free bedding materials

One of the most common forms of horse bedding is straw, but research has shown that it produces more dust than wood shavings, pellets, and shredded paper or card.  It is worthwhile looking into alternatives such as wood pellets or shavings.

Feed quality

Horses tend to bury their noses into hay, especially round bales, which exposes them to increased dust levels.  Haylage is made from grass cut earlier than hay and after drying in the field it is wrapped in plastic to retain the nutrients contained.  A recent study showed that by changing a horse’s diet to haylage can reduce dust levels dramatically.  Either way, steaming hay or haylage in a Haygain Steamer is the only proven product to kill pathogens and mould spores in forage.

Horse Feeding Methods

The method used to feed hay can also be detrimental to the air quality since the use of hay nets or racks can increase the particles of dust produced in contrast to hay laid on the floor. The horses' head is raised to an unnatural level compared with grazing outside and causes the nose and eyes to be exposed unnecessarily. 

Here are some tips to reduce the effect of dust when feeding forage.

1.    When you receive deliveries of hay bales, check for visible dust or mould that may have developed in transit.

2.    Store hay as far away as possible from the stables, in a separate waterproof building or trailer.

3.    Storage above the stalls should be avoided at all costs as it results in a constant source of dust.

4.    Persons that regularly handle a large quantity of hay should consider wearing a facemask to protect themselves from respiratory problems.  

Leaving barn doors open or closed

Leaving the stable doors open allows fresh air to be drawn in as the warm staler air is extracted either by natural or mechanical ventilation.  This will help maintain a low level of dust. It may be considered not to open the doors if the temperatures outside are lower than normal, but doing so will help to reduce dust and ammonia levels, thus providing a healthy atmosphere for the horses and grooms.

Cleaning and sweeping the stables

When it comes to cleaning out the stalls, consider turning the horses out for exercise.  Don’t move horses back into a cleaned stall for up to an hour, this gives time for any residue dust not removed to settle.  Also, you may want to consider deep cleaning every stable at least once a year (some people deep clean every few months for this reason).  This helps you manage dust but also combat the build-up of ammonia and ensure your stables have a high sanitary condition.

Methods of sweeping using a soft broom can be effective in removing larger particles of dust if used correctly.  Also, specialised hoovers are available on the market that is able to extract the dust from the air quickly and easily.

If the owner is able to construct a new barn or range of stables or is considering the renovation of an existing establishment, particular attention should be given to the best number of vents to provide the optimum air exchange rate.  An adequate number of doors, windows and roof vents are essential to maintain good air quality.   Doors and windows could remain open even in colder weather and fans placed strategically can help recirculate the stable air and avoid dust to settle.

This article makes it quite clear that the question of air quality in equine establishments is very important, so as to provide a healthy working environment for the stable hands and their equine partners.  It is suggested that good stable management is a worthwhile investment and will pay dividends for the owner and staff.