Dry weather can cause itchy, dry skin, a dry throat, and nosebleeds, and can also make people with asthma or respiratory issues feel uncomfortable—this is especially noticeable in winter, when problems like static electricity and cracks in furniture and walls may occur. Many households install a humidifier to alleviate these issues. Users must ensure that the humidity level is properly controlled—ideally between 30% and 40%. Otherwise, excessively high humidity can lead to the growth of microorganisms and the proliferation of bacteria, which may trigger allergic symptoms.

According to research by the Environmental Protection Agency (EPA), some impeller-type or ultrasonic humidifiers on the market may, due to water quality issues, release contaminants—such as microorganisms, heavy metals, and minerals—into the indoor air, causing pollution. The EPA has not yet established comprehensive guidelines regarding the impact of indoor humidifiers on indoor air quality. There are two types of humidifiers on the market that are considered relatively ideal and have lower contamination levels: Water-curtain humidifiers: These use airflow to distribute moist air throughout the home via a damp filter or similar material; such humidifiers should be equipped with a built-in drainage system. Steam humidifiers: These cool hot steam before distributing it throughout the home.

Regular maintenance, cleaning, and upkeep are essential after installing a humidifier. No humidifier is maintenance-free. If you experience any respiratory symptoms that may be caused by the humidifier, stop using it immediately and contact your family doctor.

作者：Michael Chiu，MWS，CI
本文原載於《明報日報》。