Ventilation and air hygiene parameters in horse stables
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To assess ventilation, air hygiene and the influence of ventilation on air hygiene in horse stables, 11 barns on 4 separate premises were studied during four consecutive weeks in January and February. One of the premises used mechanical ventilation and woodshavings bedding, all others used natural ventilation and straw bedding. In all barns, inside and outside temperature and relative humidity were monitored for a week. Ammonia, stall wind speed, smoke clearance, airborne micro-organisms (fungi, gram-negative bacteria and total bacteria) and stall air and breathing zone air dust and endotoxin levels were measured. The aim was to find a correlation between the inside-outside temperature difference and air hygiene parameters. In the naturally ventilated barns, inside temperature and humidity were 7.5(2.8-12.7)°C and 75(67-86)%, respectively. Ammonia ranged from <2 to 11 ppm, wind speed was <0.2 to 0.6m/s. Airborne micro-organism levels were 33561(2830-35043), 510(84-1111) and 2887(344-10809) colony forming units (CFU)/m3 for fungi, gram-negative and total bacteria, respectively in the naturally ventilated barns and 769(671-3960) and 4815(2121-6222) for fungi and total bacteria in the mechanically ventilated barns. Stall air and breathing zone air dust levels, in mg/m3, were, respectively 0.24(0.16-0.58) and 2.70(0.44-12.49) in the naturally ventilated barns, and 0.46(0.13-0.98) and 7.36(1.97-45.03) in the mechanically ventilated barns. Stall air and breathing zone air endotoxin levels, in EU/m3, were 268(86-800) and 1653(1273-48485) naturally ventilated barns, and 233(22-504) and 1974(453-15028) in the mechanically ventilated barns. Levels of dust and endotoxin were correlated (spearman correlation 0.884). Breathing zone levels of dust and endotoxin were significantly higher than and not correlated to stall air levels. CFU counts of fungi were significantly lower in the mechanically ventilated barns. No correlation between barn outside-inside temperature difference and any of the air hygiene parameters was found, most likely due to a limited number of samples and variability in used source materials.