Continuous Positive Airway Pressure (CPAP) therapy is a common treatment for obstructive sleep apnea. This therapy often includes a heated humidifier to add moisture to the pressurized air, preventing dryness in the nose, mouth, and throat and improving comfort and compliance. The humidifier works by heating water, creating vapor that is delivered through the tubing and mask to the user. Because this process involves heating and evaporating water, the type of water used in the reservoir is important for both the machine’s longevity and the user’s respiratory health.
How Minerals Damage CPAP Humidifiers
Filtered water, while seemingly cleaner than tap water, is typically insufficient for CPAP humidifiers because it does not remove dissolved minerals. When water containing minerals like calcium and magnesium is heated, the pure water evaporates, but these non-volatile solid particles are left behind. As more water evaporates, the concentration of these minerals increases, leading to calcification. This results in the formation of a hard, white residue, often called limescale, on the walls of the water chamber and the heating plate.
This mineral buildup, or scaling, interferes with the proper function of the machine. Over time, a thick layer of scale reduces the efficiency of the heating element and forces the machine to work harder to maintain the set humidity level. This reduced heat transfer means the humidifier cannot deliver the intended level of moisture, potentially leading to discomfort for the user. Furthermore, mineral deposits can compromise the integrity of the water tub, leading to the need for frequent and costly replacement of the component or even voiding the machine’s warranty.
The Requirement for Distilled Water
The universally recommended solution for CPAP machines is distilled water, a type of purified water created through vaporization and condensation. Water is boiled into steam, leaving behind all non-water substances, including minerals and solids, and the steam is then cooled and collected as pure liquid water. This process ensures the water is free from total dissolved solids (TDS). This method ensures that when the water is heated in the CPAP humidifier, only pure water vapor is produced, leaving no residue behind to damage the equipment.
This purification method is fundamentally different from standard filtration systems, such as carbon filters or pitcher filters, which are designed to remove taste and odor-causing contaminants like chlorine. While these filters may remove some impurities, they are largely ineffective at removing the dissolved minerals that cause scale buildup. Therefore, using filtered water, or even most types of bottled water, will still lead to mineral accumulation in the humidifier chamber. Distilled water’s lack of dissolved solids is the specific property that makes it the ideal choice for long-term machine maintenance and performance.
Water Quality and Respiratory Health
Beyond machine maintenance, using non-distilled water introduces a risk of introducing biological contaminants into the respiratory system. Tap and filtered water are not sterile and can harbor microorganisms such as bacteria, fungi, and mold. The warm, moist environment inside the CPAP humidifier chamber can act as a breeding ground for these pathogens, allowing them to multiply. When the CPAP machine aerosolizes the water to create humidity, any contaminants present can be carried into the air pathway and inhaled deep into the lungs. Inhaling contaminated aerosols may lead to respiratory irritation, congestion, or more serious conditions like pneumonia, particularly in individuals with underlying respiratory issues. Additionally, tap water often contains trace amounts of chemicals like chlorine, which can become aerosolized and potentially irritate sensitive airways.