Humidifier Buying Guide

The human body relies on air and humidity to help maintain a consistent internal temperature by evaporating heat moisture. Air can hold a lot of water, which can influence how a person feels if the humidity level in the air adds to the heat moisture rather than wicks it away. When the temperature drops far enough below the humidity level that everything starts drying out, the dry cold can wring out too much moisture.

Running heaters and air conditioners to keep a consistent room temperature can be especially draining on humidity levels indoors. Low humidity can cause dry skin, dry eyes, and sinus irritation, inviting trouble like illnesses or headaches. When you’re tired of the seasonal ups and downs of humidity, a good humidifier can help fight back.

What Is a Humidifier?

A humidifier is used to adjust the humidity level indoors to keep it comfortable and healthful. There are different types of humidifiers, but the basic operation of a humidifier is to turn water into mist or steam and introduce moisture back into the air.

Absolute humidity refers to the quantity of water vapor present in the air, regardless of air temperature, and this number is useful in certain technical contexts. But because temperature affects how much water vapor air can “hold,” speaking of relative humidity is more useful for how wet or dry air feels.

Relative humidity is the amount of water vapor in relation to the capacity that the air has at a particular temperature. People tend to prefer a relative humidity level above 30%. During winter in some areas, humidity levels can drop to as low as 10% or less. These are the days when you catch a chill or can’t quite get warm.

When to Use a Humidifier

Humidifiers can be useful to keep humidity levels between 30% and 50%. Below 30% humidity, the air can draw moisture out of wood furniture or flooring, resulting in damage, like warping or cracks. Wallpaper can begin to peel away as the moisture is pulled out and weakens the adhesive.

As things dry out, there’s an increase in static electricity, so people start to notice that simply walking across carpet can be a shocking experience. Humidifiers even keep houseplants greener and healthier because dry air draws moisture from the soil. They can also help when someone is already sick, as moisture in the air can ease congestion when battling coughs and colds.

Common health problems often associated with dry air include:

• Dry airways that irritate asthma and cause coughing and sore throat
• Dry skin and cracked lips
• Sinus inflammation and pain
• Headaches
• Allergies

Often, if there’s an increase in any of the symptoms above, the first preventive step you can take is to bring out the humidifier.

How a Humidifier Works

There are two main ways humidifiers introduce moisture back into the air: warm mist created using steam and cool mist created through movement and evaporation.

Warm Mist

Warm mist humidifiers boil water in the tank and then filter the steam out as a mist to add to the humidity.

They can operate more quietly than other humidifiers because the water turns into steam and doesn’t require a fan to blow the moisture into the room. The base of the humidifier gets very hot and produces scalding water, but unless you are sitting directly in front of the filter, the air has returned to room temperature by the time you can breathe it in.

While the mist evaporates to a cooler temperature, the water inside the tank and the humidifier itself are still an extra heat source, so warm mist humidifiers have the bonus of slightly warming the room around it.

Similar to the warm mist humidifier is the vaporizer. Vaporizers are often smaller and less powerful than steam humidifiers. They are designed for personal use, as their primary goal is to provide medical benefits. With vaporizers, medications or aromatherapy additives applied to a tray inside the humidifier turn into vapor with the steam.

Use warm mist humidifiers with caution, as boiling water can damage people, pets, and furniture if not carefully handled. Because of the scalding water, they are not advised for use around small children.

Cool Mist

Cool mist humidifiers are seen as the safer alternative because the mist is achieved by the movement of air and evaporation, without the hot air required for steam. The air pulled into the humidifiers is cooled by the water in the tank, and potentially cooling the air in the room.

Three common types of cool mist humidifiers include:

• Evaporative humidifiers: A wick or filter absorbs water from the tank, and a fan pulls in air from the room to push through the filter. The moisture evaporates and is pushed back into the room.
• Ultrasonic humidifiers: A nebulizer vibrates under a tank of water, with the movement agitating the water enough to create mist.
• Impeller or air washer humidifiers: A spinning disk moves water through a diffusion screen, creating a mist and removing impurities and allergens from the air.

When it comes to noise, ultrasonic humidifiers are the quietest of the cool mist humidifiers. Both evaporative and air washer humidifiers rely on fans or spinning disks that create extra noise.

Humidifier Features to Look For

There are a variety of different brands to choose from, each offering different features to better match the needs of your home. Here are a few to focus on.

Ease of Maintenance

It’s very important to find a humidifier that is easy to take care of. They will have to be cleaned regularly, which will involve safely removing and then reassembling the tank and other parts.

Look for easy-to-understand operational buttons, like power, mode, or speed. Sturdy construction and pieces that fit together smoothly will help it last. An insulated base can help make sure it won’t damage furniture it’s placed on with moisture and heat.

Ease of Use

Different humidifiers offer different features—the key is knowing which options are available so you can find the best humidifier for your home.

Included humidistat: A humidistat senses relative humidity and turns off the humidifier when the air saturation hits the appropriate humidity level or when the tank runs out of water.

Multiple speeds/output: Adjustable outputs allow you to regulate the amount of moisture and time it takes to add the right amount of humidity to the air by changing the speed of the airflow.

Indicator lights: Especially important with heat-generating humidifiers, these lights clearly indicate when the machine is powered on.

Digital displays: These present clear and useful information about the power status, the humidifier mode, and the fan settings.

Timer with automatic shut-off: If there’s no humidistat included with the unit, go with the timer to help make it easier to monitor the water levels in the tank.

Replaceable filters: Filters can be an added cost of humidifier operation. Make sure the filters are easily accessible and replaceable. 

Combination of warm and cool mist humidifiers: Some humidifiers allow you to choose between warm and cool mist modes.

Humidifier Types

There are humidifiers designed for every type of room, from a small home to a busy office building. The larger the humidifier, the better coverage it can provide. Homeowners usually need to know these three types of humidifiers.

Whole-House Humidifiers

These work in addition to your HVAC system to cover the largest possible area, often using the building’s interior ventilation systems. Because it is an evaporative system, the water tank on whole-home humidifiers is connected to the water line and automatically monitored, with no tank refills needed. Bypass humidifiers, drum humidifiers, and in-duct or furnace humidifiers are all types of whole-house humidifiers.

Console Humidifiers

These large appliances can provide air moisture to multiple rooms but are small enough to be a more portable unit. The water tanks require manual refills, so make sure you choose a model with a tank size that will fit under your sink faucet.

Tabletop Humidifiers

These single-room humidifiers are small and easily portable. They are useful in small rooms or for adding a little humidity to specific parts of rooms. They also have a manually refillable tank. It’s best to use distilled water for tabletop humidifiers, as hard water from the tap can interfere with safe operation.

Humidifiers for Different Room Sizes

The size of the room is a good way to determine the moisture output needed from a humidifier. Determine the square footage of the area that needs some adjusting, whether it’s an entire room, an entire building, or just your own personal office area, to find the humidifier size you need.

• Travel humidifiers cover small spaces, up to 25 square feet. 
• Small room humidifiers cover between 25 and 299 square feet. 
• Medium room humidifiers cover 300 to 499 square feet. 
• Large room humidifiers cover 500 to 999 square feet. 
• Whole-house console humidifiers cover areas of 1,000 square feet or more.

Warnings and Safety Precautions for Humidifiers

Too much moisture in the air will not provide any extra health benefits and can potentially be harmful. Bacteria, mold, mildew, and other dangerous microbes grow best in wet, humid places. Keep indoor humidity levels below 60% maximum to avoid excess moisture buildup on windows or walls that could become grimy or moldy in unnoticed crevices.

Dirty humidifiers can also make people sick. When the machines aren’t cared for properly, humidifier water tanks can create breeding grounds for these microbes. Follow the manufacturer’s guidelines for using and maintaining your humidifier so you don’t accidentally exacerbate symptoms or cause new ones.

A good approach to humidity control is to use a hygrometer and monitor the room when using a humidifier. A hygrometer is a digital device that measures moisture and humidity in the air and the room temperature. Look for a hygrometer to help keep the humidity level in your home in the ideal range between 30% and 50%.

The water you use in your humidifier matters for air safety as well, particularly in ultrasonic room humidifiers. Because these break up water particles, they’ll also split mineral particles in tap water and disperse them into the tank and into the room’s air, leaving a “white dust” of mineral residue that people are breathing in. If the manufacturer specifies using distilled water for your humidifier, or a water demineralization filter or cartridge, don’t ignore these directions.

How to Clean Your Humidifier

Everyone in your home will breathe air affected by your humidifier. If you’re not following manufacturer cleaning instructions often enough, the unit can grow mildew, mold, and other bacteria and then pump that into the room with the mist. To keep your home and air safer, clean the humidifier regularly: before and after every use.

Weekly or multiple times a month—depending on how often you use the humidifier—descale, clean, and dry all parts of the humidifier. Between uses, don’t let water sit in the machine. A film can form that can breed bacteria in the enclosed tank. If you’re skipping a day of use, empty the water and clean and dry the tank.

If you won’t be using your humidifier for a long period of time, clean and dry the humidifier thoroughly before putting it into storage and then again before you use it after storage.

Humidifier Cleaning Tips

• Take apart the humidifier and use 1 cup of white vinegar and a toothbrush to scrub down all accessible areas of the machine parts.
• Pour 1 tablespoon of bleach in the tank and add 1 complete tank of water. Shake the tank to be sure the sides of the tank are descaled and covered. Let the water and bleach mix rest in the tank for 20 minutes. Rinse the tank out completely and repeatedly, until any smell is gone, to make sure harmful chemicals don’t get released into your indoor air.

Humidifiers and Essential Oils

A common question is whether or not you can use essential oils in a humidifier to introduce the oils into the air you breathe. Not all humidifiers are compatible with essential oils, so this might not be as good an idea as it could seem on the surface. Make sure to double-check labels and read the owner’s manual to know for sure that the humidifier is compatible with oils.

Some important points about essential oils and humidifiers:

• Essential oils will not diffuse as well in a humidifier because humidifiers are not designed to break down the water and oils together, which can leave larger droplets of oil escaping and making a mess or damaging furniture.
• Certain oils can deteriorate the plastic parts of a humidifier. It’s particularly important to avoid citrus-based oils (such as lemon, lime, or grapefruit).
• Warm mist humidifiers will be too hot for the essential oil to survive. The boiling water will purify the oil and it won’t have much of an aroma left.
• With care, essential oils can be used with some ultrasonic humidifiers. They are very similar in design to the smaller essential oil diffusers; however, a diffuser is specifically designed to provide the best delivery of the essential oils.