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
Humidity per hour: X = Air changes per hour (ACPH) * M³ * density of air * humidity ratio Humidity per day: X * 24 The air changes per hour (ACPH) ranges widely, based on: Ventilation: Values may be obtained from the HVAC maintainer that routinely (typically every third year or so) 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 kg/m3 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 50 m2 (540 sq ft) with closed windows (wood isolation) may consume 36.72 litres per day (9.70 U.S. gallons per day) to raise the relative humidity from 20% to 55%: 24 * 1.53 L/h (2 * 1 × 125 m3 × 1.2 kg/m3 × 0.0051):
Air changes per hour Ventilation: 2 Insulation leakage: 1 (a few windows) Cubic meters: 125 m3 (50 m2 * 2.5 m height) Density of air: Typically 1.2 kg/m3 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 Prevention of dermatitis: Low humidity can cause adverse health effects and may cause atopic dermatitis, and seborrhoeic dermatitis. Management of hair loss: Commonly, patients with seborrhoeic dermatitis experience mild redness, scaly skin lesions and in some cases hair loss. Prevention of dry mucous membranes and cough: drying out mucous membranes such as the lining of the nose and throat may lead to a snoring problem, and can cause respiratory distress. Prevention of dry eye syndrome. Improved apparent temperature: The heat index and humidex measure the effect of humidity on the perception of temperatures above +27 °C (81 °F). In humid conditions, the air feels much hotter, because less perspiration evaporates from the skin.
Improved climate for material 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 (humidifier lung). 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 (RH). 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 (ASHRAE) 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 (like fungus gnats) in houseplants may indicate overwatering. Hanging laundry will increase the humidity.
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