For each of the 20 to 24 sites that were suspected of having a high bacterial contamination of the air and the surface of equipment and facilities, 4 subsites evenly arranged in each site were designated along each step of the entire hatchery from the egg receiving room to the chick counting room. For the air samples, plate count agar (Difco, Detroit, MI), Endo agar (Difco), and Sabouraud dextrose agar (Difco) were used for aerobic bacteria, coliform, and fungi, respectively. Three agar plates were prepared that had been exposed for 10 min (compared with 1 min in operating hatcher). In addition, a Rodac agar plate (TPC: KM0808, Han-il Komed, Gyeonggi-do, Korea) and another Rodac agar plate (ECC: KM0802, Han-il Komed) were prepared for the surfaces of the equipment and facilities and were used for aerobic bacteria and coliform, respectively. Two agar plates were stamped to the surface of the equipment and facilities. After being transported to the laboratory, each plate was incubated at 37°C for 24 to
48 h, and then a count of the colonies on the plate surface was done, yielding colony-forming units/63.6 cm2 and colony-forming units/16 cm2, respectively.