Continuous Positive Airway Pressure (CPAP) therapy delivers pressurized air to manage sleep apnea. Many CPAP devices use a heated humidifier to add moisture to the airflow, improving comfort and preventing dryness. The water used in this chamber is a frequent concern for users, especially regarding the safety of distilled water past its expiration date. Understanding the specific purpose of the water and the nature of the “expiration” date is helpful for maintaining both health and equipment.
The Function of Distilled Water in CPAP Machines
Distilled water is the only type recommended by CPAP manufacturers for mechanical reasons. The distillation process involves boiling water into steam and condensing it back into a liquid state, which effectively removes all dissolved minerals, metals, and contaminants. Tap water and even purified water contain trace minerals, such as calcium and magnesium, that do not evaporate with the water.
When mineral-containing water is heated in the CPAP humidifier, the pure water turns into vapor, but the mineral solids are left behind. Over time, these remnants accumulate on the heating plate and chamber walls, forming hard scale or mineral deposits. This buildup reduces the efficiency of the humidifier and can lead to machine damage. Using distilled water prevents this scaling, ensuring the device functions efficiently and prolonging the life of the machine’s components.
What “Expired” Means for Bottled Water Purity
The expiration date on a bottle of distilled water does not mean the water molecules have chemically broken down. Water does not spoil in the traditional sense because it contains no sugars or proteins for microorganisms to consume. The date is instead related to the integrity of the plastic packaging over time.
Plastic containers can degrade over years, potentially allowing trace chemicals to leach from the plastic into the ultra-pure water. The expiration date also accounts for the possibility of minor imperfections in the seal or micro-fissures in the plastic. These flaws could allow external contaminants, such as airborne microorganisms or dust, to enter and compromise the water’s initial purity. The date serves as a manufacturer’s guarantee of purity based on packaging stability.
Health and Equipment Risks of Using Compromised Water
Using expired or contaminated water in a CPAP humidifier introduces two primary risks: harm to the user’s health and damage to the machine. The greatest health concern is the possibility of microbial contamination. While distilled water is initially pathogen-free, bacteria, fungi, or mold can be introduced if the container seal is compromised or if the water is stored improperly.
When the CPAP machine heats this water, any present microorganisms are aerosolized, creating a fine mist inhaled directly into the user’s respiratory tract. This direct exposure increases the risk of respiratory infections, such as bronchitis or pneumonia. Furthermore, if “expired” water was contaminated with trace minerals from poor storage, it could still lead to the accelerated formation of scale. This scaling impairs the humidifier’s function and potentially voids the machine’s warranty.
Best Practices for CPAP Water Management
To safeguard both health and equipment, always prioritize using freshly opened, high-quality distilled water. If distilled water is unavailable in an emergency, purified bottled water can be used temporarily, but only as a short-term solution. In such cases, the humidifier chamber must be cleaned meticulously the following morning to remove any potential mineral residue.
The water in the humidifier chamber should be emptied every morning after use, and the chamber should be allowed to air-dry completely. Never leave standing water in the chamber between uses, as this significantly increases the risk of microbial growth. Store unopened containers of distilled water in a cool, dark location to preserve the integrity of the plastic packaging and minimize contamination.