Cruise ships could learn from China's pig hotels' ventilation systems to help prevent contamination Half kidding, I don't know if it's realistic.  I was surprised to read about China's pig hotels which are much cleaner than the disgusting wet markets that are so popular for the locals. China's multi-story hog hotels elevate industrial farms to new levels The ventilation system is designed to prevent air from circulating between floors or to other buildings. Air enters through ground channels and passes through ventilation ducts on each level. The ducts are connected to a central exhaust on the roof, with powerful extraction fans pulling the air through filters and pushing it out of 15-meter high chimneys.