humidifiers bacteria fine particulate matter pm2.5 · Apr 26, 2022

Are you using a humidifier? Take these precautions against bacteria, mold and fine particulates (PM2.5)

We at HypoAir are big proponents of getting the humidity in your house or office to a good range (40-60%) and for those with a dry air problem, have recommended humidifiers. We wanted to make you aware of a few problems that can occur if they are not regularly cleaned or the wrong water is used.

As I discussed in other posts, the concentration of water vapor present in the air is called humidity. Too little water vapor is low humidity, which can cause dryness in the respiratory system, sinuses, and ability for viruses to survive and infect for longer in the air. Injecting the air with water vapor raises the humidity to the proper level (40-60%). Humidifiers essentially create water vapor and eject it into the air.

There are several types of humidifiers out there. Consumer Reports lists four types of portable humidifiers: Cool Mist Evaporative, Cool Mist Ultrasonic, Warm Mist Humidifiers (also known as steam vaporizers), and Dual Mist. They are all subject to microbial growth (bacteria/fungus) if they are not cleaned regularly, which can lead to serious respiratory infections like humidifier lung (only one humidifier did not emit bacteria into the air: the evaporative or wick humidifier). If you don’t have the manufacturer’s instructions, humidifiers should be cleaned at least once a week. Many websites will recommend a bleach solution, but there’s no good reason to release these harmful vapors in your home when there are safer options:

Empty out the tank and disassemble the parts that normally come apart. To clean, here is our suggestion:
- Clean from microbes: Use Total Clean or Force of Nature to clean all parts of the tank and base, using a soft toothbrush to get into hard to reach places. Rinse with water.
- Clean from scale buildup: Use 1 cup white vinegar plus 1 cup water in the tank and the base and let it soak for 20 minutes to loosen any mineral scale buildup, then scrub with the toothbrush, rinse thoroughly and let them air dry.
- Note: cleaning with vinegar alone does not kill all bacteria and fungus (see our post on non-toxic cleaners).
With evaporative humidifiers, remove and rinse the filter/wick, and let it thoroughly air dry.

That’s it–no mysteries here! You have a clean humidifier, ready for use to add that satisfying mist of clean moisture to your air, right? Well, yes, but here is the caution: despite having become very popular because of their quiet, efficient operation, ultrasonic humidifiers can transfer whatever minerals and particles are present in your water, into the air. That mist may not be just water vapor, but also calcium, magnesium, sodium, and other dissolved solids. Normally these minerals are not harmful on their own to our bodies, but we were not meant to breathe in such particles. In one study at the University of Alberta, operating an ultrasonic humidifier with tap water resulted in particulate matter concentration equivalent to a polluted city (!). In the study, the humidifier was placed in an upper-story bedroom, but fine particulate matter (PM2.5) was distributed throughout the house via central air circulation. “These particles are so small that they can evade our filtration system in the upper airway and penetrate deep into our respiratory tract,” explained Chester Lau, lead author of the paper. “Upon doing so, they also send chemical species associated with them into our bodies. Using dirty or contaminated water could cause further detrimental health impacts.”

Of course, the best solution would be to use distilled water purchased from the grocery store, or filtered water from a filter that removes Total Dissolved Solids, such as ZeroWater, in ultrasonic humidifiers. Not all water filters remove minerals and other dissolved solids, so you’ll need to be careful what type of filtered water you use. Also, you should consider the cost of using distilled or highly filtered water in your humidifier, because it can add up.

Here's the bottom line: humidity is great in the proper doses, just make sure that it’s not carrying bacteria, mold or fine particulates with it!

Photo by Artem Kovalev on Unsplash

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