A dehumidifier is an appliance designed to improve indoor air quality by removing excess moisture from the air. The device draws in humid air, passes it over cold coils to condense water vapor, and collects the water in a reservoir before releasing drier air back into the room. While its purpose is to prevent issues like mold growth and dust mites that thrive in high humidity, a dehumidifier can inadvertently cause sickness if not used or maintained correctly. Health risks fall into two categories: contamination originating from the machine itself and the physiological consequences of over-drying the air.
When the Unit Itself Becomes a Problem
The most direct way a dehumidifier can cause illness is when the standing water in its collection reservoir is neglected. This water provides a warm, nutrient-rich environment that is an ideal breeding ground for microorganisms, including mold, mildew, and harmful bacteria. This stagnant water can become contaminated with bacteria such as Legionella pneumophila, the organism responsible for Legionnaires’ disease.
If the contaminated water is allowed to sit, these microbes can become aerosolized and dispersed back into the indoor air as the dehumidifier operates. Inhaling these fine, bacteria-filled water droplets can lead to respiratory illnesses like Legionnaires’ disease or the milder, flu-like Pontiac fever. Even without a serious infection, the presence of mold and mildew spores can trigger allergic reactions, exacerbate asthma symptoms, and lead to conditions like hypersensitivity pneumonitis in sensitive individuals.
Health Effects of Overly Dry Air
Running a dehumidifier too aggressively can lead to excessively dry air. Relative humidity levels that drop below 30% are considered too low and negatively affect human physiology. Low humidity primarily impacts the body’s natural defense mechanisms, particularly the mucous membranes lining the respiratory tract.
When these membranes dry out, their ability to trap and flush out airborne pathogens, dust, and irritants is significantly reduced. This impairment of the mucociliary clearance system makes a person more susceptible to common cold and flu viruses, which also tend to survive longer in dry, cool conditions. Overly dry air can irritate the eyes, causing dryness and discomfort. Furthermore, low humidity contributes to chapped lips, dry skin, and the exacerbation of pre-existing issues like eczema.
Maintaining Optimal Indoor Humidity
Preventing dehumidifier-related sickness requires maintaining a controlled indoor environment. The optimal range for human health and comfort is typically between 40% and 50% relative humidity. Monitoring these levels accurately is necessary, which can be accomplished with a simple device known as a hygrometer.
To prevent the growth of harmful pathogens in the unit, the water collection reservoir should be emptied daily, or at least every few days. A deep cleaning of the tank is recommended every two to three weeks. For cleaning, a disinfecting solution of equal parts white vinegar and water is effective at killing mold and bacteria without the potential damage or fumes associated with bleach.
The air filter should also be inspected and cleaned or replaced every few months to ensure proper airflow and prevent the circulation of dust and spores. Correct placement is important; the unit should be positioned away from walls and obstructions to allow for adequate air circulation. By maintaining the target 40% to 50% humidity range and following a consistent cleaning schedule, users can maximize the air quality benefits while mitigating health risks.