Air quality is VERY important in the hatchery and air FLOW even more. The “dirty zone” (where chicks are) should have a negative pressure compared to the “clean zone” (where eggs are) to prevent microbes (and esp. spores of Aspergillus) to cause cross-contamination. Hence regular airplating is paramount. And often, fogging (aeral disinfection) can be of big help to reduce air contamination.