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HUMIDIFIERS

Humidifiers:

A humidifier is a household appliance that increases humidity (moisture) in a single

room or in the entire house. There are point-of-use humidifiers, which are commonly used to

humidify a single room, and whole-house or furnace humidifiers, which connect to a home's

HVAC system to provide humidity to the entire house.

Types of humidifiers:

There are different types of humidifiers which are given below

Evaporative humidifiers

The most common humidifier, an "evaporative", "cool mist", or "wick humidifier", consists ofjust a few basic parts: a reservoir, wickand fan. The wick is a filter that absorbs water from the

reservoir and provides a larger surface area for it to evaporate from. The fan is adjacent to thewick and blows air onto the wick to aid in the evaporation of the water. Evaporation from the

wick is dependent on relative humidity. A room with low humidity will have a higherevaporation rate compared to a room with high humidity. Therefore, this type of humidifier is

self-regulating: As the humidity of the room increases, the water vapor output naturallydecreases. These wicks become moldy if they are not dried out completely between fillings, and

become filled with mineral deposits over time. They regularly need rinsing or replacementif


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this does not happen, air cannot pass through them, and the humidifier stops humidifying thearea it is in and the water in the tank remains at the same level.

Vaporizer (Steam Humidifier) (Warm Mist Humidifier) Boils water, releasing steam and moisture into the air. A medicated inhalant can also be

added to the steam vapor to help reduce coughs. Vaporizers may be more healthful than cool

mist types of humidifiers because steam is less likely to convey mineral impurities ormicroorganisms from the standing water in the reservoir. Boiling water requires significantly

more energy than other techniques. The heat source in poorly-designed humidifiers can overheat,causing the product to melt, leak, and start fires.


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Impeller Humidifier (Cool Mist Humidifier) A rotating disc flings water at a diffuser, which breaks the water into fine droplets that float intothe air.

Ultrasonic Humidifier:

A metal diaphragm vibrating at an ultrasonic frequency creates water droplets thatsilently exit the humidifier in the form of a cool fog. Unlike the humidifiers that boil water, these

water droplets contain any impurities that are in the reservoir, including minerals from hardwater (which then forms a white dust on nearby objects), and pathogens growing in the stagnant

tank. Ultrasonic Humidifiers should be cleaned regularly to avoid bacterial contamination which

may be projected into the air.

Impeller and ultrasonic humidifiers do not selectively put water in the air, they also add anysuspended material in the water to the air such as microorganisms and minerals. The amount of

minerals and other materials can be greatly reduced by using distilled water, though no water isabsolutely pure. Filters may also reduce the amount of material but the EPA warns, "the ability

of these devices to remove minerals may vary widely."[1] Depending on the volume, this dustmay have negative health effects. Wick humidifiers trap the mineral deposits in the wick;

vaporizer types tend to collect minerals on or around the heating element and require regularcleaning with vinegar or citric acid to control buildup.


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Forced-Air Humidifiers (whole-house)

For buildings with a forced-air furnace, a humidifier may be installed into the furnace. They canalso protect wooden objects, antiques and other furnishings which may be sensitive to damage

from overly dry air. In colder months, they may provide substantial energy savings, since ashumidity increases, occupants feel warm at a lower temperature. Bypass humidifiers are

connected between the heated and cold air return ducts, using the pressure difference betweenthese ducts to cause some heated air to make a bypass through the humidifier and return to the

furnace. The humidifier should usually be disabled during the summer months if air conditioningis used; air conditioners partially function b reducing indoor humidity.


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Common styles:

y Drum style (bypass): A pipe brings water directly to a reservoir (a pan) attached to thefurnace. The water level in the pan is controlled by a float valve, similar to a small toilet

tank float. The wick is typically a foam pad mounted on a drum and attached to a small

motor; hot air enters the drum at one end and is forced to leave through the sides of thedrum. When the hygrostat calls for humidity, the motor is turned on causing the drum torotate slowly through the pan of water and preventing the foam pad from drying out.

Advantages include:

y Low costy Inexpensive maintenance (drum-style pads are cheap and readily available)

Disadvantages include:

y Requirement for frequent (approximately monthly) inspections of cleanliness andpad condition

yWater evaporation even when humidification is not required (due to the pan ofwater which remains exposed to a high velocity air stream)

y Mold growth in the pan full of water (this problem is exacerbated by the largequantity of air, inevitably carrying mold spores, passing through the humidifier

whether in use or not).

For the latter reason especially, drum-style humidifiers should always be turned off at the

water supply during summer (air conditioning) months, and should always be used with high

quality furnace air filters (MERV ratings as high as possible to ensure small numbers of moldspores reaching the humidifier's pan) when the water supply is turned on.


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yDisc Wheel Style:Very similar in design to the drum style humidifiers, this type of furnace

humidifier replaces the foam drum with a number of plastic discs with small grooves on

both sides. This allows for a very large evaporative surface area, without requiring a great

deal of space. Unlike the drum style humidifiers, the disc wheel does not need replacing.

Advantages include:

y Very low maintenance (basin of humidifier should be cleaned out periodically,unless automatic flushing device is installed)

y No regular replacement of parts necessaryy Higher output due to large evaporative surface areay Can be installed in hard water situationsy Maintains efficiency throughout lifespan


y Higher priceyWater evaporation even when humidification is not required (due to the pan of

water which remains exposed to a high velocity air stream)

y Bypass Flow-Through Style:A pipe brings water directly to an electrically-controlled valve at the top of the

humidifier. Air passes through an aluminum "biscuit" (often called a pad; using the term

"biscuit" to emphasize the solid rather than foamy form) which is similar to a piece of

extremely coarse steel wool. The biscuit has a coating of a matte ceramic, resulting in anextremely large surface area within a small space. When the hygrostat calls for humidity,the valve is opened and causes a spray of water onto the biscuit. Hot air is passed through

the biscuit, causing the water to evaporate from the pad and be carried into the building.


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Advantages include:

y Reduced maintenance (new biscuit only when clogged with dust or mineraldeposits, typically once per year)

y Lack of a pan of potentially stagnant water to serve as a breeding ground for moldas with a drum-style humidifier

y No incidental humidification caused by a constantly-replenished pan of water in ahigh velocity air stream

y Reduced requirement for expensive air filtersy Uses little electricity


y A somewhat higher purchase pricey Manufacturer and model-specific replacement biscuits versus the relatively

generic drum-style pads

y A portion of the water supplied to the unit is not evaporated. This can generate aconsiderable amount of waste water, and does require connection to a drain.

y Spray Mist Type:

A pipe, usually a small plastic tube, brings water directly to an electrically-controlled valve in the humidifier. Water mist is sprayed directly into the supply air, andthe mist is carried into the premises by the air flow.


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Advantages include:

y Low cost.y Simpler than bypass types to install - single cut hole for installation, no additional

ducting.

y Uses little electricity.y Small, compact unit - fits where other types cannot. (Approx 6 inches square.)y Because it does not require bypass ducting it does not undermine the pressure

separation (and therefore, blower efficiency) of the return and supply ducts.

y Does not require use of moisture pads (on-going expense).y Highly efficient usage of water. Does not generate waste water and does not

require separate connection to a drain.y Requires little maintenance. Periodic cleaning of nozzle may be required in hard

water environments.

y Lack of a pan of potentially stagnant water to serve as a breeding ground for moldas with a drum-style humidifier.


y Spray nozzle can become clogged in hard water situations, necessitating the useof water filter, periodic cleaning of nozzle, or nozzle replacement.

y Additional types: 'Non-Bypass Flow-Through' (fan augmented), 'Steam', 'Impeller orCentrifugal

Atomizer' and 'Under Duct'.

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