Airborne contamination of 8 beef abattoirs was characterized considering the air treatment systems in place. Based on the data acquired, thresholds in line with the bibliography were proposed for controlling total viable counts. For all abattoirs, airborne contamination by total viable counts and Enterobacteriaceae decreases from bleeding to carcass cooling. Total viable counts contamination levels in the “dirty” areas (bleeding, dehairing) differed little between slaughterhouses, exceeding 3.2 log CFU/m3. In “clean” areas (evisceration to cooling), contamination is more variable, illustrating the impact of the abattoir configuration on airborne contamination. Air treatment systems provide added value to control air flows in dehiding, trimming and weighing areas, compared with extractions alone. Nevertheless, these systems that control airflows are necessary but not sufficient. The physical separation of clean from dirty areas, the positions of extraction fans in the clean area to extract steam from carcasses and from equipment like steam vacuum, air leaks from the hair tripery to the clean area need to be considered. The use of F9 filters in air treatment systems to microbiologically treat outside air blown into the clean zone limits the variability of total flora contamination. But, like other configurations, it remains higher than that of the outside air (2.4 log CFU/m3).