Home Humidifiers: EPA Statement on Indoor Air Quality

While the Federal government has not found any serious health risks posed by home humidifiers, the Environmental Protection Agency (EPA) has released a statement on the harmful potential of certain types of humidifiers. According to the EPA, increased air moisture may promote the growth of microorganisms and bacteria in the air or on surfaces. Furthermore, some humidifiers may release potentially harmful minerals into the air. Read on to learn a bit more about the health issues surrounding humidifiers and how to prevent them.

Mineral and Microorganism Dispersal

The primary means by which humidifiers can negatively impact indoor air quality is via mineral and microorganism dispersal. Microorganisms may grow in the standing water of a tabletop or central humidifier. When this water is vaporized, the bacteria and other microorganisms are carried along with it. Likewise, minerals present in hard water (or water with a high level of total dissolved solids) can also be dispersed through vapor. Minerals can accumulate within the humidifier—which exacerbates bacteria growth—or it can be carried into the air and then deposited on surfaces throughout the home. This can be seen as white dust that can irritate those with sensitive respiratory systems.

Types of Home Humidifiers

There are four main types of home humidifiers: ultrasonic, impeller, evaporative, and steam vaporizer. Of these types, ultrasonic and impeller are believed by the EPA to produce the greatest dispersions of microorganisms and mineral deposits. When tested by the EPA, the steam vaporizer did not release a substantial amount of minerals or microorganisms. The EPA has not yet tested evaporative vaporizers.

Water and Home Humidifiers

The best way to reduce the mineral content of vaporized water is to use distilled water. Tap water, particularly in rural areas, can be very hard. Distilled water still contains some minerals but its mineral content is significantly lower than most tap water. Deionized water and water that has been treated through reverse osmosis is also low in minerals. Be careful when buying bottled water, however, as not all water has been treated to remove minerals.

Clean and Care of Humidifiers

In addition to using distilled water rather than tap water, the EPA recommends proper clean and care of your humidifier to prevent mineral and microorganism build-up. The EPA lays out the following care and uses guidelines:

Empty your home humidifier tank once a day. Wipe it dry and refill it with clean water.

Clean the entire humidifier every three days. Use a solution of 3 percent hydrogen peroxide on any areas that are touched by water. Use a small brush to clean any scaling, mineral deposits, or build up. Rinse and dry thoroughly.

For central home humidifiers, do not allow water to stand in the tank for an extended period of time. After the humidifier season, empty and clean humidifier tanks thoroughly before storing.

Do not humidify indoor environments beyond 50 percent humidity, as this promotes bacteria growth.

Also, remember to unplug your humidifier whenever cleaning or maintaining.

In conclusion, there is likely no serious threat to your health through the normal use of any type of home humidifier. Though certain types of home humidifiers have been identified by the EPA as potentially more dangerous, through proper care and use, you can minimize any adverse impacts. As always, discontinue use and consult a doctor if you exhibit any respiratory systems from using your home humidifier system.

Types of Whole House Humidifiers

If you own your home and need to humidify multiple rooms, a central home humidifier is likely the right choice for you. Whole-house humidifiers, while greater in upfront costs, are more cost-effective in the long run. Plus, they get better performance per dollar than comparable single room humidifiers and can add value to your home as well. But once the decision to get a whole-house humidifier is made, it’s time to choose the type of central humidifying system for your home. There are three main types of whole-house humidifiers:

Drum Whole House Humidifiers

Drum systems are the least expensive among central humidifier systems, but there is more upkeep involved. With these humidifiers, a foam or fabric drum pad is partially submerged in the water reservoir. It rotates within the reservoir via a motor. Air from your heating system enters the reservoir and passes over the wet drum pad, which picks up moisture and carries it throughout your home. Because of the materials and machinery used, you’ll have to regularly clean your water reservoir and change your belt in order to prevent mildew, mold, bacteria and mineral buildup.

Flow-through Home Humidifiers

Flow-through systems address the problems of a standing water reservoir by using a rectangular foam or aluminum pad. Water drips onto the pad and heated air flows through the pad, picking up moisture along the way. Excess water is drained away. These systems are less susceptible to mold growth, but the pad can get clogged if it isn’t replaced or cleaned regularly. These setups are better for basements with floor drains in order to collect the water run-off.

Spray Mist Home Humidifiers

The spray mist system is more sophisticated. An electronic mister sprays water vapor directly into the heated air whenever the heating system kicks in. Because of the technology involved, these systems are a bit more expensive. Plus, if you have hard water—such as the water found in most municipal and well water supplies—you won’t be able to hook right into your regular plumbing since mineral buildup and impurities will clog the mist heads. You may instead need to fill up a reservoir with distilled water. Spray mist home humidifiers work best with oil-fired or gas-fired heating systems.

Other Options

Aside from the type of humidifier, you can also choose whether to include a fan, a humidistat and a bypass gate. Fans are needed if your system is installed on the hot air supply side of your ventilation system. Spray systems also require fans. You can forgo a fan by installing the system on the cold-air return duct. Humidistats are useful as they let you adjust the humidity in your home to your preference in the same way a thermostat adjusts the temperature. The bypass gate is useful because it allows you to disable your humidifier during the summer months when you do not need the added humidity.

Choosing a System

Based on your budget, water supply, furnace type and HVAC system, the decision on which type of whole house humidifier often makes itself. Still, you may want to consult a professional and price out your options before moving forward.

Impeller Home Humidifiers

Impeller home humidifiers add humid air into a room by atomizing water into vapor with a spinning disk. Unlike steam humidifiers, which boil water into vapor, and evaporative

humidifiers, which pass air through a wet medium, impeller humidifiers are typically unfiltered.

How Impeller Humidifiers Work

Impeller humidifiers use very basic technology. Water is sprayed through a spinning disk, which separates the water into tiny droplets. The water vapor is then propelled into the room, humidifying the air.

Advantages of an Impeller Humidifier

Impeller humidifiers are affordable, portable, and easy to set up. The only maintenance involved in an impeller is refilling the reservoir and keeping it clean. There are typically no filters, cartridges, or wicks to replace. There is also no heating element, which allows an impeller to consume less electricity.

Disadvantages of an Impeller Humidifier

Impeller humidifiers are notorious for dispersing “white dust.” White dust is a particulate matter containing minerals and microorganisms. This white dust is carried into the room via the water vapor and collects on surfaces once it settles. If inhaled, this white dust may be harmful to children, the elderly, or those with respiratory disease. Because of this, many reviewers discourage the use of impeller humidifiers altogether. White dust is more of an issue in areas with very hard water and can be prevented by using distilled water and cleaning the tank regularly.

Other Considerations

Because impeller humidifiers use the same mechanism to create water vapor as it does to propel it into the air, these units do not typically have adjustable speeds. With evaporative and fan-driven humidifiers, the lower settings are useful for quieter operations. Impeller humidifiers do not often have such options. Impeller humidifiers are also classified as cool mist humidifiers. The vapor from an impeller humidifier is not heated and therefore may make the room feel a bit cooler. But on the plus side, with no heating element, impeller humidifiers are safer and do not carry the risk of scalding.


Impeller humidifiers are one of the least expensive models on the market. They work efficiently with very high outputs and very little electricity consumption. However, in areas with hard water and in households with individuals sensitive to allergens and respiratory irritants, and impeller humidifier may not be a good fit due to its susceptibility to white dust. With proper care and maintenance, however, impeller humidifiers can be safely operated.


Home Humidifier Filters

Many consumers overlook a very important aspect when buying a home humidifier: filters. On of some models of home humidifiers, filters are essential to their operation. These filters must be replaced occasionally, which can introduce a couple of issues that can be avoided if you shop smart. Read on to learn some key tips for buying home humidifier filters.

Why do humidifiers need filters?

This is a good question—especially since not every home humidifier needs a filter. The answer is hard water. Without filters, home humidifiers would release minerals, impurities, bacteria, and anything else that was present in your water right into the air. Of course, one might argue that if the water is safe to drink, it is safe to breathe. But the truth of the matter is that many home humidifier owners are less than diligent when cleaning and maintaining their home humidifiers. As such, the water in the reservoir can remain stagnant and promote mold, mildew, algae, and bacteria growth.

With that being said, not all home humidifiers need filters. Some impeller and ultrasonic humidifiers do not use filters—though they should (avoid cool mist humidifiers without filters). Steam humidifiers and vaporizers also do not use filters, as the water is boiled to remove bacteria. Evaporative wick humidifiers must have filters or some kind of wet medium, as it is integral to their operation.

How often should I change my home humidifier filter?

It depends. For best guidance, read through the documentation that comes with your humidifier. But as a rule of thumb, buy a new filter every one to two months. Or, while cleaning your humidifier regularly, pull out the filter and look at it. If it has mold growth, mineral deposits, or any other visible buildup, it’s time for a change. You can likely get a little bit more life out of your filter by rinsing it from time to time, but it’s safer and easier to simply replace it.

Where do I find home humidifier filters?

That’s the million-dollar question. The issue is that many of the cheaper or clearance home humidifiers you’ll get at Target or Wal-Mart are marked down because they are being discontinued. As such, it can be extremely difficult to find replacement filters. We recommend buying a pack or two of replacement filters at the time of purchase—because next year, they may be nowhere to be found.

How much do home humidifier filters cost?

It varies, but in most cases, it’s more than you’d expect. Manufacturers make big money on aftermarket purchases of filters, cartridges, and other necessities for a home humidifier. Follow our advice above and buy filters at the same time you buy the humidifier. This will let you know if you’re getting into an expensive, long-term relationship with your home humidifier and its filters. Some filters can cost up to $10 to $20 each. Others are more affordable and come in packs of two or three.

Can I use generic filters in my home humidifier?

Probably not. Home humidifiers come in numerous different models and designs from various brands and manufacturers. It’s highly unlikely that a Honeywell humidifier filter will fit in a Holmes humidifier. And if it did, it probably would not perform up to standards. Unless the packaging clearly states that is compatible with the exact make and model of your home humidifier, then it probably won’t fit.

Home humidifier filters are a necessary inconvenience with most systems and devices. Because of this, it’s in your best interest to think ahead, stock up, and shop smart.


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