Answer:
Over the past 10 to 15 years many new technologies have been introduced in the heating, ventilation and air conditioning industry. One technology that is important for reducing airborne pathogens (germs) is ultraviolet energy. Ultraviolet disinfection of airborne organisms by use of free-standing air purifiers or a built-in UV system reduces allergy-causing fungi and molds (mold is one of 5 most common allergens).
Electronic air cleaners are especially important in bedrooms to remove microorganisms, mold spores and viral contaminants. Many people even travel with a portable air cleaner because hotel rooms can contain many airborne pathogens.