• SafBaby blog post on humidifiers baby sleeping in crib next to humidifier

SafBaby’s Healthy Building and Indoor Environmental Expert, Mary Cordaro, has been creating healthy homes and living spaces for over 25 years. She is recognized as a world leader for her holistic approach to solving complex issues created by environmental contaminants.

Mary has helped hundreds of people, from prospective parents who want their baby to begin life in a healthy home, to children and adults suffering from allergies, asthma, mold, chemical and electrical sensitivities, who need to find and safely remediate the toxic triggers that have caused their illness.

Part 1 of this series covered the unknown or ignored realities of humidifier use: the impact of using impure water, high-tech humidifier units and the growth of mold and unwanted microorganisms in a home.

In this Part 2, Mary Cordaro shares her insights and guidelines on how to find the healthiest humidifier and use it in the healthiest way. The following are her recommendations to help you decrease the chances of polluting your indoor air and avoid making your child’s short – and long-term health worse.

Types of Humidifiers

There are five kinds of humidifiers: warm-mist, evaporative, ultrasonic and impeller humidifiers and steam vaporizers. Each kind works differently. There are stand-alone units, room units (portable) and whole-house humidifiers which are often integrated into the blower system of the furnace.

Steam vaporizers have a heating element that boils water to release steam, resulting in a warm mist.

Warm-mist humidifiers produce hot water vapor in the same way as a steam vaporizer but mix the vapor with the cool air in the room before emitting it. Models that contain an internal fan are the most effective at mixing the air and vapor.

Evaporative humidifiers produce humidity by pushing air through a moistened absorbent material, i.e. a filter or wick. Some evaporative humidifiers use a pump to recirculate the water throughout the unit. These are called recirculating evaporative humidifiers. Both kinds of evaporative humidifiers produce a cool mist.

Ultrasonic humidifiers typically use a metal or ceramic diaphragm that vibrates at an ultrasonic frequency to create water droplets. These can produce a cool or warm mist.

Impeller humidifiers use a spinning disc to spray water at high speed onto a diffuser which breaks the water into microscopic droplets that are diffused into the air. These produce a cool mist.

SafBaby blog post on humidifiers little boy in bed blowing nose

Healthiest Choices 

The healthiest humidifiers are stand-alone steam and warm-mist humidifiers vaporizers. By boiling the water, bacteria and mold that may be inside the unit are killed or inactivated and therefore do not attach to the water molecules that make up the steam produced. A study completed in 1989 at the Oak Ridge Tennessee National Laboratories confirmed this when they found that warm-mist units released insignificant amounts of bacteria.

Exercise Extreme Caution!
These units can be a burn hazard if they accidentally tip over.
Take safety precautions to make sure this doesn’t happen.

Do not ever leave a child unattended when a humidifier is being used.

The other three types of humidifiers should be avoided: Evaporative, Ultrasonic, Impeller and all whole-house systems. Here’s why:

The Problem with Evaporative Humidifiers

According to Dr. Howard Smith, a Harvard-trained pediatric ear, nose and throat doctor and attending surgeon at Connecticut Children’s Medical Center in Hartford, Connecticut, evaporative humidifiers “are like paint sprayers, and they take whatever is in the water reservoir and make a droplet out of it. Unfortunately, even distilled water placed in non-sterile reservoirs will grow bacteria after a few hours and the mold in the crevices of such containers are ready to spring to life immediately.”

The Problem with Ultrasonic Humidifiers

Dr. Smith points out that ultrasonic humidifiers are even worse than evaporative humidifiers. “They ‘weaponize’ the droplets by making them so small that they waft down into the lungs rather than stopping in the nasal passages, sinuses, middle ear spaces, and larger airways.”

Also, take into consideration the results of a 2015 study published in Environmental Engineering Science that found that 90% of drinking water contaminants in ultrasonic humidifier aerosols are inhalable including minerals and metals.

A similar conclusion was drawn back in 1988 by EPA scientists who found that “ultrasonic machines can fill the household air with tiny particles of minerals and pieces of microorganisms that can be inhaled deep into the lungs, where they may cause allergies or illness.”  Such impurities can include lead, asbestos, aluminum, dissolved organic gases – even radon. Using tap water makes the problem especially severe.  The study showed that “particle levels in a closed bedroom could exceed the Federal standard for particles in outdoor air by nearly 50 times.”

The Problem with Impeller and Whole House Humidifiers

The American Lung Association Health House Guidelines state that impeller models are similarly problematic in that they can disperse unwanted organisms into the air.

Whole house humidifiers are not ideal because any humidifier needs to be cleaned frequently and impeccably to avoid the growth of unwanted organisms. It is very unlikely that a person will clean the unit as often and as thoroughly as it should be.

With rare exceptions, I also do not recommend humidification added to central forced-air furnace and AC systems (which is delivered through the ducting) not only because of the potential for moisture issues, but also because most heating and AC systems contain dust and debris which can become moldy when moisture is added to it.

Avoid Units Advertised as Antimicrobial. The filters in evaporative humidifiers are often treated with antimicrobial chemicals in an effort to slow the growth of mold and bacteria. The reservoirs of humidifiers are also often treated with antimicrobials such as Microban, triclosan or nano silver. Nano silver is a heavy toxin and if absorbed through the skin or inhaled can deeply imbed into the lung tissue and other organs. Avoid all if possible. Note that any humidifier that says it prevents mold or bacteria or has special clean technology is likely to be treated with a toxic chemical or nano silver to achieve this result. However, the only way to know for certain is to call the company and ask. 

Try to purchase a humidifier that is BPA-and BPS-free to avoid hormone disrupting chemicals.  Unfortunately, this may not be possible unless the unit is completely or mostly made of metal.

SafBaby blog post on humidifiers little girl sleeping in bed

Healthiest Usage

Use the Cleanest Water. Fill the humidifier with either purified water from a well-maintained reverse osmosis (RO) system or use distilled water. Do not use tap water even if you have a whole house filter. You might think that tap water is ok to use as long as you purchase a warm-mist humidifier or vaporizer that boils all the impurities off. This is not necessarily the case.

According to Sarah Janssen, MD, PhD, MPH, a science fellow at the Natural Resources Defense Council, boiling tap water “will not solve the problem” of traces of drugs and medicines that have been found in our drinking water. “Home filtering systems such as reverse osmosis may reduce the medication levels,” says Timothy Bartrand, PhD, a postdoctoral fellow at Drexel University, Philadelphia.

Even distilled water may be an issue. The 1988 study published in Environmental Science and Technology, a journal of the American Chemical Society, acknowledged that most people do not follow the manufacturer’s instructions to use distilled water, but even if they did, “a large number of fine particles – twice the single-day standard – can fill the air.”

Keep Indoor Humidity at or Below 50%. According to some, including Dr. Smith, the ideal range for nasal and sinus clearance is between 40-50%. To help measure the amount of moisture in a space, a hygrometer is recommended.

A word of caution: the number on the hygrometer is not necessarily the most accurate read of the actual humidity in the whole room or even where your child might be. There are many, many conditions in homes that affect indoor levels of relative humidity that vary from climate region to climate region. The point is, every room and house is different and using a hygrometer is only a rough estimate of actual conditions. Hygrometers can be purchased at hardware or department stores.  

On some humidifiers, there is a feature called a humidistat that measures the humidity in the room and adjusts the humidifier’s output to keep the humidity within a specified range. However, humidistats are not always accurate and often do not reflect the actual relative humidity in the room. 

Dry Out and Clean Daily. Every day the humidifier is in use, dry it thoroughly and use 3% hydrogen peroxide to clean it. Pay special attention to the holding tank. The moist, warm environment of a humidifier is a perfect breeding ground for bacteria and fungi.

The Best Approach 

Dry air at home can certainly worsen a child’s symptoms or delay them from getting better. But, using a humidifier can carry its own serious consequences.

In fact, doctors that specialize in children’s breathing advise not using humidifiers.

Dr. Robin Deterding of Children’s Hospital Colorado is the Medical Director at their Innovation Center, Chief of Pediatric Pulmonary Medicine, Chair of their Interstitial Lung Disease Research Network and Director of their Breathing Institute. Her advice: don’t use a humidifier.

And if you suspect mold in your home or have never had a mold inspection to confirm the absence of mold, definitely do not use a humidifier.

Be Smart and Know that Using a Humidifier Must Be Done Responsibly

If you are going to purchase a humidifier, think of buying one as part of a safer package to include RO water and 3% hydrogen peroxide. Then follow the guidelines below to do the least harm.

  1. Choose stand-alone warm-mist humidifiers or steam vaporizers free of antimicrobials and BPA.
  2. Use distilled or reverse osmosis water.
  3. Clean daily and thoroughly with 3% hydrogen peroxide. Dry thoroughly.
  4. Use a hygrometer to monitor the humidity level. Keep it between 40-50%; too much humidity is actually detrimental.
  5. Make sure the humidifier or vaporizer is in a safe place and has no chance of tipping over. Be aware that children will be curious about the steam coming out and want to get near it which can result in severe burns.
Don’t Miss Part 1: 4 Must-Ask Questions Before Using a Humidifier

About Mary Cordaro, SafBaby’s Healthy Building and Indoor Environmental Expert

Mary Cordaro is President of Mary Cordaro, Inc. a consulting firm she founded in 1989, specializing in healthy building and remodeling; diagnosing and solving toxic contaminant problems in homes and workplaces; and educating about healthy building practices and non-toxic lifestyles.

Since becoming certified in the German field of Baubiologie* in 1992, Mary has gained national prominence for her integrity and meticulous adherence to the highest standards of health for homes. These standards go far beyond “green certifications” to embrace the most sensitive people, including the developing fetus, as well as the overall health of the Earth.

Mary Cordaro’s integrated approach to creating a healthy environment is unique. To determine the source of a complex problem quickly and accurately, Mary specifies healthy building and interior materials and products, and directs a team of highly experienced specialists and scientists in the fields of mold and moisture, EMFs, chemicals, water, heating, air conditioning and ventilation, and building science.

Mary shares her vast knowledge of environmental health topics through speaking engagements at professional conferences as well as online webinars.

She also has a growing following of health practitioners, medical doctors, parents, architects, environmentalists and design professionals who understand the enormous health benefits of shifting away from environmental toxins.

For more information, visit Mary’s website and blog.

*Baubiologie is the study of how the built environment affects human and planetary health.

Editor’s Note: This article was originally posted in April 2016 and has been reviewed and updated.

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