Editing Humidifier (section)

==Overview==

===Humidification calculation===
[[File:Ceiling vent.jpg|thumb|Ventilation determines most of the [[air changes per hour]] in a space without windows.]]

: 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 wildly based on:
** [[Ventilation (architecture)|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 [[Blower door#Airflow at a specified building pressure|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 {{convert|50|m2|sqft|abbr=on}} with closed windows (wood isolation) may consume {{convert|36.72|L/d|U.S.gal/d|abbr=off}} to raise the relative humidity from 20% to 55%: 24 * 1,53 L/h (2*1×125×1.2×0.0051):
* Air changes per hour
** Ventilation: 2
** Insulation leakage: 1 (a few windows)
* Cubic meters: 125 m<sup>3</sup> (50 m<sup>2</sup> * 2.5 m height)
* [[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 climate]]s, 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.<ref name="cpsc.gov">{{cite web |url=https://www.cpsc.gov/safety-education/safety-guides/home/the-inside-story-a-guide-to-indoor-air-quality/ |title=The Inside Story: A Guide to Indoor Air Quality |publisher=[[U.S. Consumer Product Safety Commission]] |archive-url=https://web.archive.org/web/20210322041034/https://www.cpsc.gov/safety-education/safety-guides/home/the-inside-story-a-guide-to-indoor-air-quality/ |archive-date=22 March 2021 |url-status=live}}</ref>

====Health treatment====
* Prevention of dermatitis: Low humidity can cause adverse health effects and may cause [[atopic dermatitis]],<ref>{{cite journal |last1=Engebretsen |first1=KA |last2=Johansen |first2=JD |last3=Kezic |first3=S |last4=Linneberg |first4=A |last5=Thyssen |first5=JP |title=The effect of environmental humidity and temperature on skin barrier function and dermatitis. |journal=Journal of the European Academy of Dermatology and Venereology |date=February 2016 |volume=30 |issue=2 |pages=223–49 |doi=10.1111/jdv.13301 |pmid=26449379|s2cid=12378072 |doi-access=free }}</ref> and [[seborrhoeic dermatitis]].<ref>{{cite journal |last1=Araya |first1=M |last2=Kulthanan |first2=K |last3=Jiamton |first3=S |title=Clinical Characteristics and Quality of Life of Seborrheic Dermatitis Patients in a Tropical Country. |journal=Indian Journal of Dermatology |date=September 2015 |volume=60 |issue=5 |pages=519 |doi=10.4103/0019-5154.164410 |pmid=26538714|pmc=4601435 |doi-access=free }}</ref>
** [[Management of hair loss#Humidifier|Management of hair loss]]: Commonly, patients with [[seborrhoeic dermatitis]] experience mild redness, scaly skin lesions and in some cases [[hair loss]].<ref>{{cite web|url=http://www.mamashealth.com/skin/seb.asp|title=What is Seborrheic Dermatitis?|access-date=June 11, 2010|url-status=live|archive-url=https://web.archive.org/web/20100420023503/http://www.mamashealth.com/skin/seb.asp|archive-date=April 20, 2010}}</ref>
* Prevention of dry [[mucous membrane]]s and [[cough]]: By drying out mucous membranes such as the lining of the nose and throat, it may also lead to a snoring problem, and can cause [[respiratory distress]].<ref>{{Cite journal|last2=Juvonen|first2=R.|last3=Jokelainen|first3=J.|last4=Harju|first4=T. H.|last5=Peitso|first5=A.|last6=Bloigu|first6=A.|last7=Silvennoinen-Kassinen|first7=S.|last8=Leinonen|first8=M.|last9=Hassi|first9=J.|year=2009|title=Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections|journal=Respiratory Medicine|volume=103|issue=3|pages=456–62|doi=10.1016/j.rmed.2008.09.011|pmid=18977127|last1=Mäkinen|first1=T. M.|doi-access=free}}</ref>
* Prevention of [[dry eye syndrome]].
* Improved [[apparent temperature]]: The [[heat index]] and [[humidex]] measure the effect of humidity on the perception of temperatures above {{convert|+27|C|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.<ref>{{Cite book|url=https://books.google.com/books?id=xfB99Kf38MwC&q=low+humidity+wooden+furniture&pg=PA490|title=Home Comforts: The Art and Science of Keeping House|last=Mendelson|first=Cheryl|date=17 May 2005|publisher=Simon and Schuster|isbn=9780743272865|language=en}}</ref> Books, papers, and artworks may shrink or warp and become brittle in very low humidity.<ref>{{Cite book|url=https://books.google.com/books?id=e68FaiCRjIoC&q=low+humidity+books+artwork&pg=PA118|title=Disaster Response and Planning for Libraries|last=Kahn|first=Miriam B.|date=1 January 2012|publisher=American Library Association|isbn=9780838911518|language=en}}</ref>

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.<ref>{{Cite book|url=https://books.google.com/books?id=mkPYKXcwsrAC&q=static+electricity+humidity&pg=PA34|title=Secret of Electricity|last=Elsersawi|first=Amin|date=2012-06-15|publisher=AuthorHouse|isbn=9781477216200|language=en}}</ref>

===Negative impact of overuse of humidifiers===
{{see also|Dehumidifier}}

An indoor relative humidity of less than 51% resulted in significant reductions in mite and allergen levels.<ref>{{cite journal |last1=Arlian |first1=LG |last2=Neal |first2=JS |last3=Morgan |first3=MS |last4=Vyszenski-Moher |first4=DL |last5=Rapp |first5=CM |last6=Alexander |first6=AK |title=Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates. |journal=The Journal of Allergy and Clinical Immunology |date=January 2001 |volume=107 |issue=1 |pages=99–104 |doi=10.1067/mai.2001.112119 |pmid=11149998|doi-access=free }}</ref> 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).<ref>{{cite journal|last=Baur|first=X|year=1988|title=Humidifier lung and humidifier fever|journal=Lung|volume=166|issue=2|pages=113–124|doi=10.1007/BF02714035|pmid=3130530|s2cid=23430270|display-authors=etal}}</ref> 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.<ref name="cpsc.gov" />

A [[dehumidifier]] can be used to balance the humidity.