How Humidifiers Can Lead to Poor IAQ

Indoor air quality (IAQ) plays a crucial role in the health and comfort of families, especially when sickness hits home. In a recent case from the Midwest, a simple oversight in humidifier use led to a significant deterioration in air quality, unbeknownst to the household. Much like how using the wrong ingredients in cooking can spoil a dish, using regular hard water instead of distilled water in an ultrasonic humidifier had unintended consequences on the family’s HVAC system and IAQ.

Why It Matters: The Science Behind It

This case centers around a household with children who had fallen ill. On the recommendation of their doctor, the family began using a humidifier to alleviate symptoms and improve comfort levels. However, instead of using distilled water as advised by the manufacturer, they filled the humidifier with regular tap water — a common mistake that many (or most!) are unaware can drastically affect indoor air quality.

Humidifiers come in various types, with ultrasonic and evaporative being two of the most common. Both have their benefits, but they work in very different ways — and as this case illustrates, the type of humidifier and water used can have a significant impact on indoor air quality.

Ultrasonic Humidifiers:

These devices use high-frequency sound waves to vibrate a metal diaphragm, breaking water into a fine mist. While this method is energy-efficient, it also atomizes everything in the water, including minerals like calcium and magnesium, if tap water is used. The harder the water, the higher the mineral content. When these minerals are released into the air as PM2.5 (fine particulate matter that can reach deep into the lungs), they can degrade air quality and contribute to filter clogging, as seen in this case study.

Evaporative Humidifiers:

In contrast, evaporative humidifiers rely on a more natural process. They use a fan to blow air through a wet wick or filter, or with heat which causes the water to evaporate and add moisture to the air. Because evaporative humidifiers rely on evaporation, only pure water is dispersed into the air. Minerals in hard water are left behind in the wick, meaning there’s no risk of releasing mineral particulates into the air. However, over time, the wick or filter will need to be replaced due to mineral buildup or mold starts building up.

While both types of humidifiers increase indoor humidity, the use of hard water in ultrasonic models poses a unique challenge. The family in this case used an ultrasonic humidifier with regular tap water, leading to the release of hard minerals into the air.

When the air quality monitor detected poor air quality, the Sensi thermostat automatically circulated air through the HVAC system, ensuring the filter had the chance to clean the air in the home of fine particles from the Ultrasonic Humidifier. If the air recirculation fan hadn’t turned on, the air quality in the home would have been far worse.

A Closer Look: Data Analysis

The family began to notice that every night between 8 pm and 6 am — while the humidifier was running — there were spikes in PM2.5 levels, measured by the Woosh’s air quality monitor which measures PM2.5 and PM10 (a measure of particle size). Over a period of just seven days, the Woosh’s smart air filter detected a differential pressure increase of more than 50%, signaling that the filter was becoming clogged. It was later determined that the cause of the filter clogging and poor air quality was from the mineral particles from the humidifier. These minerals not only impacted air quality but also reduced the efficiency of their HVAC system.

Adding to the effectiveness of the system, Woosh’s integration with the Sensi smart thermostat played a critical role in maintaining safe air quality levels.

PM2.5 (fine particulate matter) Spikes:

Every night starting November 4th, 2023, PM2.5 levels shot up as the humidifier atomized hard minerals from the tap water.

Increased Pressure Drop Across the Filter:

Over time, the filter became more clogged with mineral particles, causing a steady rise in differential pressure. As the filter loaded up, its ability to process air decreased, leading to more severe PM2.5 spikes.

Combining both charts, you can see the interplay between indoor air quality and pressure drop across the filter over time. You’ll notice the IAQ spikes get continually worse every night as the filter becomes more clogged. This is because as the filters start to clog the HVAC system delivers less and less air flow, resulting in less efficient air filtering.

As the data analysis showed, Woosh’s smart monitoring system allowed the family to detect these issues in real time. The combination of continuous monitoring, the automatic air circulation triggered by the Sensi thermostat, and the data-driven insights helped them identify the root cause of the problem and take corrective action before the system became fully compromised. Had they not noticed the problem, the filter would have become completely clogged, adding additional stress to the recirculation blower and other parts of the HVAC which could cause early system failure. Meanwhile, the air quality would have become out of control due to little or no air flow through the system.

Preventing the Problem: A Simple Fix

The solution is straightforward: always use distilled water or demineralization tablets/cartridges in ultrasonic humidifiers. By doing so, you eliminate the risk of atomizing hard minerals into PM2.5 because the distillation process (or the demineralization tablets) removes these minerals from the water. This keeps both your indoor air quality and your HVAC system in good shape.

Moreover, the value of smart air filter technology, such as Woosh’s, is clear. Without the real-time data from the air quality monitor and the ability to automatically turn on the HVAC air circulation fan via the Sensi smart thermostat, this family would not have been aware of the problem until it caused significant damage or impacted their health. The system’s smart features provided timely alerts of poor air quality and a full air filter, allowing the family to address the issue before more serious consequences occurred.

It is also important to note that “time-based” or “visual inspection” methods of filter changes would have not been effective in this case. As shown in the differential pressure data, the filter life was relatively unchanged while in use for several weeks. Once the humidifier was used, the filter loaded up to capacity in just 7 days. So filter change frequency depends on particulate loading, not simply “change it every 3 months”. And since calcium dust is white in color, it wouldn’t be noticeable by visually inspecting the air filter. 

The Woosh smart air filter’s ability to detect when a filter is beginning to get full, alert the user, and automatically send a replacement filter is a game changer for the industry.

Conclusion

This case serves as a reminder that seemingly small decisions — such as the type of water used in a humidifier — can have far-reaching effects on air quality and system efficiency. With the right tools and knowledge, homeowners can ensure that their living environments remain healthy and their HVAC systems perform optimally.

Fortunately for this family, Woosh’s smart air filter, air quality monitor, and Sensi smart thermostat integration provided the necessary insights and adjustments to keep the air quality safe, and avoid long-term damage to their HVAC system.