Short answers, pulled from the story.
Absolute humidity measures the mass of water vapor divided by the volume of air, expressed in grams per cubic meter. Relative humidity expresses this state as a percentage comparing current water vapor levels against the maximum possible for that specific temperature and pressure.
Maintaining indoor relative humidity above 40% significantly reduces the infectivity of aerosolized influenza virus while extremely low relative humidities below 20% cause tissue lining nasal passages to dry and crack. Infants living in homes with mold face a much greater risk of developing asthma and allergic rhinitis than those in drier environments.
When relative humidity approaches 100%, condensation can occur on surfaces leading to corrosion decay and safety risks like frozen emergency exits. Buildings with foundations not properly sealed allow water to flow through masonry pores via capillary action compromising structural integrity over time.
Pilots must calculate takeoff distances accounting for high humidity because it requires longer runways and decreases climb performance significantly. Cold humid air promotes ice formation which affects wing profiles and increases weight creating danger for naturally aspirated internal combustion engines where ice may form inside carburetors.
Optimal humidity for electronic devices sits between 30% and 65% balancing the need to avoid brittleness from dry air against conductivity issues from excess moisture. Data centers monitor relative humidity levels closely to prevent spontaneous shutdowns caused by static electricity buildup in very low humidity environments below 30%.