BFH-HAFL, Direction des institutions, de l’agriculture et des forêts (DIAF), B+M AGROTECH

Horsekeeping: Influence of Three different Ventilation Systems on Stable Climate

Stable climate has an important impact on the respiratory health of horses. In a study on indoor climate quality, three different ventilation systems were tested.

Stable climate

Natural ventilation in stables is not always sufficient to ensure a climate that meets the needs of the animals; its effectiveness depends on the natural air circulation in the building. Various models of mechanical fans are available on the market to improve stable climate. They allow the temperature and humidity of the air to be regulated and dust and harmful gases to be removed by means of adequate air movement. These systems are very important, as too high a concentration of aerosols in the air can, for example, lead to reduced performance and respiratory diseases in horses. To ensure a suitable climate for the animals, the following climate parameters should be within certain ranges:

  • temperature: 5-25 °C (Martin-Rosset 2012)
  • relative humidity: 50-80 % (FSVO)
  • air flow: 0.1 to 0.4 m/s (FSVO)
  • ammoniac (NH3): < 10 ppm (FSVO)
  • carbon dioxide (CO2): < 1000 ppm (FSVO)

In order to comply with these criteria, the air should be changed completely between four and eight times per hour.

Experimental measurement of ammonia and carbon dioxide emissions

In this study, three ventilation systems (ceiling fans (V1), axial fans (V2), tube ventilation (V3)) were tested in an indoor stable and compared with natural ventilation (V0). Temperature (T), relative air humidity (RH), air velocity, carbon dioxide (CO2) and ammonia (NH3) were measured for each system and related to the activity of the horses. The microclimatic indicators were measured in three horse boxes at the breathing height of the horse (1 m) (fig.1). The climate of the stable used for the trial was measured for five consecutive days with each system.

Figure 1: Placement and protection of CO2, NH3, T and RH sensors in the horse boxes under the feed trough. (Photo: BFH-HAFL)

Key findings

  • Horses are the main source of CO2 in a stable. An increase in their activity caused by human activity leads to an increase in emissions.
  • Temperature, relative humidity and horse activity influence the CO2 and NH3 content of the air. After taking into account the activity of the horses, the average CO2 values (ppm) modelled were below the recommended limit of 1000 ppm (V0 = 867.7; V1= 755.1; V2 = 511.9; V3 = 595.7). 
  • The highest NH3 concentration measured was 2.8 ppm, below the recommended 10 ppm. These low values are partly due to the low temperatures during the test (<16 °C).
  • Tube ventilation (V3) was the only system that significantly (p<0.001) lowered the modelled CO2 content regardless of horse activity (fig. 2). This is due to its overpressure system which does not allow for any return air. 
Figure 2: Comparison of the four systems using a scale of scores. The system with the highest total score is the most satisfactory (3 = most satisfactory / 1 = least satisfactory / 0 = no effect). Results that do not have the same letter are statistically different.


  • Ventilation systems improve the climate in old buildings with low ceilings or poor air circulation.
  • Tube ventilation was the most efficient system in this trial.
  • Tube ventilation can be particularly recommended in elongated stables typical of individual box systems.
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