Humidifier


A humidifier is a household appliance or device designed to increase the moisture level in the air within a room or an enclosed space. It achieves this by emitting water droplets or steam into the surrounding air, thereby raising the humidity.
In the home, point-of-use humidifiers are commonly used to humidify a single room, while whole-house or furnace humidifiers, which connect to a home's HVAC system, provide humidity to the entire house. Medical ventilators often include humidifiers for increased patient comfort. Large humidifiers are used in commercial, institutional, or industrial contexts, often as part of a larger HVAC system.

Overview

Humidification calculation

  • The air changes per hour ranges wildly based on:
  • * Ventilation: Values may be obtained from the HVAC maintainer that routinely tests the ventilation of the residence.
  • * Insulation leakage: Measured with a standard blower door test.
  • Cubic meters: The volume of the room, excluding the bathroom that should be kept closed since it ventilates humidity.
  • Density of air: Typically 1.2 for dry air.
  • Humidity
  • * Current relative humidity: 20%
  • * Humidity needed to reach 55%: 35%
  • ** Humidity ratio for 35%: 0.0051
For example, a typical modern apartment of with closed windows may consume to raise the relative humidity from 20% to 55%: 24 * 1,53 L/h :
  • Air changes per hour
  • * Ventilation: 2
  • * Insulation leakage: 1
  • Cubic meters: 125 m3
  • Density of air: Typically 1.2 for dry air.
  • Humidity
  • * Current relative humidity: 20%
  • * Humidity needed to reach 55%: 35%
  • ** Humidity ratio for 35%: 0.0051

    Prevention of low indoor humidity

Low humidity may occur in hot, dry desert climates, or indoors in artificially heated spaces. In winter, especially when cold outside air is heated indoors, the humidity may drop to as low as 10–20%. A relative humidity of 30% to 50% is recommended for most homes.

Health treatment

Low humidity can affect wooden furniture, causing shrinkage and loose joints or cracking of pieces. Books, papers, and artworks may shrink or warp and become brittle in very low humidity.
In addition, static electricity may become a problem in conditions of low humidity, destroying semiconductor devices, causing static cling of textiles, and causing dust and small particles to stick stubbornly to electrically charged surfaces.

Negative impact of overuse of humidifiers

An indoor relative humidity of less than 51% resulted in significant reductions in mite and allergen levels. Overuse of a humidifier can raise the relative humidity to excessive levels, promoting the growth of dust mites and mold, and can also cause hypersensitivity pneumonitis. A properly installed and located hygrostat should be used to monitor and control humidity levels automatically, or a well-informed and conscientious human operator must constantly check for correct humidity levels.
A humidity below 50% can prevent water condensation on building materials.
A dehumidifier can be used to balance the humidity.

Humidifiers

Industrial humidifiers are used when a specific humidity level must be maintained to prevent static electricity buildup, preserve material properties, and ensure a comfortable and healthy environment for workers or residents.
Static problems are prevalent in industries such as packaging, printing, paper, plastics, textiles, electronics, automotive manufacturing and pharmaceuticals. Friction can produce static buildup and sparks when humidity is below 45% relative humidity. Between 45% and 55% RH, static builds up at reduced levels, while humidity above 55% RH ensures that static will never build up. The American Society of Heating, Refrigerating and Air Conditioning Engineers has traditionally recommended a range of 45–55% RH in data centers to prevent sparks that can damage IT equipment. Humidifiers are also used by manufacturers of semiconductors and in hospital operating rooms.
Printers and paper manufacturers use humidifiers to prevent shrinkage and paper curl. Humidifiers are needed in cold storage rooms to preserve the freshness of food against the dryness caused by hot temperatures. Art museums use humidifiers to protect sensitive works of art, especially in exhibition galleries, where they combat the dryness caused by heating for the comfort of visitors during winter.

Natural humidifiers

Natural humidifiers don't use or need a demineralization filter because the water is slowly evaporated which leaves the mineral deposit at the bottom of the container. However, natural humidifiers raise the humidity very slowly even if their water surface area is large.

Common sources

  • Human water losses, both respiratory, and insensible water loss like sweat, range in average 0.75 L/d in sedentary adults. However, most people do not spend most of the day at home.
  • Houseplants may also be used as natural humidifiers, especially if they are placed in fabric flowerpots, since they evaporate water into the air through transpiration. Care must still be taken to prevent bacteria or mold in the soil from growing to excessive levels, or from dispersing into the air. The presence of sciarids in houseplants may indicate overwatering.
  • Hanging laundry will increase the humidity.

    Homemade

One type of evaporative humidifier makes use of just a reservoir and wick. Sometimes called a "natural humidifier", these are usually non-commercial devices that can be assembled at little or no cost.
One version of a natural humidifier uses a stainless steel bowl, partially filled with water, covered by a towel. A waterproof weight is used to sink the towel in the center of the bowl. There is no need for a fan, because the water spreads through the towel by capillary action and the towel surface area is large enough to provide for rapid evaporation. The stainless steel bowl is much easier to clean than typical humidifier water tanks. This, in combination with daily or every other day replacement of the towel and periodic laundering, can control the problem of mold and bacteria.

Electric humidifiers

Evaporative humidifiers

An "evaporative", "cool moisture", or "wick humidifier", consists of just three basic parts: a reservoir, a wick, and a fan.
The wick is made of a porous material that absorbs water from the reservoir and provides a larger surface area for it to evaporate from. The fan is adjacent to the wick and blows air onto the wet 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 higher evaporation rate compared to a room with high humidity. Therefore, this type of humidifier is partially self-regulating; as the humidity of the room increases, the water vapor output naturally decreases.
These wicks become moldy if they are not dried out completely between fillings, and become saturated with mineral deposits over time. They regularly need rinsing or replacement; if this does not happen, air cannot pass through them, and humidifier stops humidifying the area it is in and the water in the tank remains at the same level.
Evaporative humidifiers function similarly to evaporative coolers.

Impeller humidifiers

humidifiers are usually noisier than others. It uses a rotating disc to fling water at a diffuser, which breaks the water into fine droplets that float into the air. The water supply must be kept scrupulously clean, or there is a risk of spreading bacteria or mold into the air.

Ultrasonic humidifiers

An ultrasonic humidifier uses a ceramic diaphragm vibrating at an ultrasonic frequency to create water droplets that silently exit the humidifier in the form of cool fog. Usually the mist gets forced out by a tiny fan, while some ultra mini models have no fans. The models without fans are meant mainly for personal use. Ultrasonic humidifiers use a piezoelectric transducer to create a high frequency mechanical oscillation in a film of water. This forms an extremely fine mist of droplets about one micron in diameter, that is quickly evaporated into the air flow.
Unlike the humidifiers that boil water, these water droplets will contain any impurities that are in the reservoir, including minerals from hard water. Any pathogens growing in the stagnant tank will also be dispersed in the air. Ultrasonic humidifiers should be cleaned regularly to prevent bacterial contamination from being spread throughout the air.
The amount of minerals and other materials can be greatly reduced by using distilled water. Special disposable demineralization cartridges may also reduce the amount of airborne material, but the EPA warns, "the ability of these devices to remove minerals may vary widely." The mineral dust may 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 regular cleaning with vinegar or citric acid to control buildup.

Steam Humidifiers

Steam humidifiers, or warm mist humidifiers, are equipped with a heating element.
A medicated inhalant can also be added to the steam vapor to help reduce cough. Vaporizers may be healthier than cool mist types of humidifiers because steam is less likely to convey mineral impurities or microorganisms from the standing water in the reservoir. However, 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.