The continuous positive airway pressure (CPAP) machine is a standard treatment for obstructive sleep apnea, delivering pressurized air through a mask to keep the airway open during sleep. Many CPAP users rely on a heated humidifier, which introduces moisture to the airflow to prevent dryness and irritation in the nasal passages and throat. The standard recommendation for this humidifier is the exclusive use of distilled water. This requirement exists because distillation removes nearly all dissolved solids and impurities found in other water sources. Using any water other than distilled water introduces foreign substances into the machine, leading to equipment damage and potential inhalation risks.
Damage to CPAP Components
The most immediate consequence of using non-distilled water is the physical deterioration of the humidifier chamber and heating element. Tap water contains various dissolved minerals, most commonly calcium and magnesium, which are responsible for water hardness. When the humidifier heats the water to create vapor, the pure water evaporates, but these non-volatile minerals are left behind. Over time, this results in the formation of mineral deposits, often called scale or limescale, appearing as a white or chalky residue on the water tank and heating plate.
This mineral buildup acts as an insulator, significantly reducing the efficiency of the heating element. The machine must work harder and longer to achieve the desired humidity level, which can eventually lead to premature failure of the heating element or the entire humidifier unit. Scale can also begin to clog the small air vents, tubing, or internal mechanisms designed to regulate humidity and pressure. The cumulative effect of this physical damage reduces the overall lifespan of the CPAP equipment and compromises the effectiveness of the therapy. Furthermore, manufacturers often stipulate that the use of non-distilled water constitutes improper maintenance, which can void the equipment’s warranty, leaving the user financially responsible for repairs or replacement.
Inhalation Risks
Beyond the threat to the equipment, using non-distilled water introduces contaminants that can be aerosolized and inhaled directly into the respiratory system. Tap water, while safe for drinking, is not sterile and often contains microorganisms such as bacteria, fungi, and protozoa. Pathogens like Pseudomonas aeruginosa and free-living amoebae, including Acanthamoeba, can be present. When the water is heated and converted into a fine mist by the humidifier, these microbes become airborne and are delivered straight into the lungs and deep respiratory passages.
Unlike the digestive tract, which possesses strong acids and immune defenses, the lungs are highly vulnerable to these inhaled contaminants. This direct exposure can lead to respiratory tract infections, which may present with symptoms similar to pneumonia, such as a cough or chest discomfort. Municipal tap water also contains chemical additives, such as chlorine and fluoride, used for disinfection. When this water is heated and aerosolized, these chemicals are also inhaled, which can cause irritation to the sensitive linings of the airways. Moreover, as mineral scale accumulates and dries, tiny particles of this mineral dust can break off and be carried into the mask, further irritating lung tissue upon inhalation.
Temporary Solutions and Cleaning Protocols
In situations where distilled water is temporarily unavailable, such as during travel, the best short-term alternative is sterile water, which is medically purified. A less ideal but functional alternative is to boil tap water for at least three to five minutes and then allow it to cool completely before pouring it into the humidifier chamber. Boiling effectively kills most microorganisms, thereby addressing the immediate biological risk. However, boiling does not remove the minerals, meaning that the risk of scale buildup in the machine remains, making this a solution for a day or two at most. Filtered or bottled drinking water is not a recommended alternative because it still contains mineral content and is not guaranteed to be sterile enough for inhalation.
If non-distilled water must be used even briefly, the humidifier chamber requires immediate and rigorous cleaning. To remove mineral deposits that have already formed, a common and effective cleaning method involves soaking the chamber in a solution of white vinegar and water. A mixture of one part vinegar to two parts water is sufficient to dissolve the scale. The chamber should soak for approximately 30 minutes to a few hours, then be thoroughly rinsed with distilled water and allowed to air-dry completely before the next use. Regular, diligent cleaning is necessary to mitigate the risks associated with temporary use of non-distilled water.