Humidifiers add moisture to indoor air, providing relief for dry skin, sinuses, and throats. The quality of the water used is directly linked to the machine’s performance and the air quality you breathe. When you purchase bottled distilled water, you will notice an expiration date printed on the container. This date is less about the water itself and more about the container and the potential for contamination over time.
The Purpose of Distilled Water in Humidifiers
Distilled water is recommended for humidifiers because it is nearly free of Total Dissolved Solids (TDS), the inorganic minerals found in tap water. The distillation process involves boiling the water into steam and then condensing it back into a liquid, which leaves behind almost all solid impurities like calcium and magnesium. Tap water contains varying levels of these minerals, which are left behind when the water is converted into mist or vapor by the humidifier.
In ultrasonic and impeller humidifiers, these residual minerals are dispersed into the air as “white dust.” This dust can settle on nearby surfaces and the microscopic particles can be inhaled. The mineral content in tap water also creates scale buildup, coating the heating elements or ultrasonic plates inside the device. This buildup reduces the humidifier’s efficiency and shortens its operational lifespan.
Understanding Water Expiration Dates
The concept of an expiration date on bottled distilled water can be misleading because pure water itself is a chemically stable compound that does not spoil. The date printed on the bottle primarily refers to the integrity of the plastic container over time. Manufacturers use this date as an assurance of quality, reflecting the point at which the plastic may begin to degrade or leach trace chemicals into the water.
If the plastic bottle is stored improperly, such as in direct sunlight or high heat, the degradation process is accelerated, potentially allowing compounds like Bisphenol A (BPA) to leach into the water. Once the bottle’s seal is broken, the primary risk becomes microbial contamination from the air. Airborne mold spores or bacteria can enter the water, where they may begin to multiply. This transition from pure, sealed water to potentially contaminated water is the true cause for concern regarding an “expired” bottle that has been opened.
Health Risks of Using Contaminated Water
The most significant danger of using old or contaminated water is the risk of aerosolizing microbial contaminants directly into your breathing air. Humidifiers can become ideal breeding grounds for bacteria, fungi, and mold because they provide a dark, moist, and warm environment. When the device runs, it acts as a nebulizer, effectively spraying these microorganisms and their byproducts throughout the room.
Inhaling this contaminated mist can lead to respiratory irritation, flu-like symptoms, or more serious infections. Of particular concern is “humidifier lung,” which is a form of hypersensitivity pneumonitis (HP). HP is an inflammatory lung disease triggered by repeated exposure to an inhaled antigen, such as the bacteria or fungi growing in the humidifier tank. Symptoms like cough, shortness of breath, and fever may develop several hours after exposure.
Safest Options for Humidifier Use
When addressing expired distilled water, the safest approach depends on the packaging’s status. If the bottle is past its expiration date but remains unopened and has been stored in a cool, dark location, the water is likely still suitable for use, as the microbial risk is low. However, if the seal has been broken or the bottle has been sitting open for an extended period, it should be discarded due to the high potential for airborne microbial contamination.
The best practice remains using freshly purchased, sealed distilled water to guarantee the lowest mineral and microbial content. Reverse osmosis (RO) filtered water is a strong alternative, as it is highly effective at removing dissolved solids. Regardless of the water source, regular and thorough cleaning of the humidifier tank every few days is the most important action to prevent the growth and dispersal of harmful organisms.