The document discusses the importance of proper humidity levels in healthcare facilities. Maintaining relative humidity between 40-60% can help reduce the spread of infections and pathogens. Low humidity allows microorganisms to grow and spread more easily through air. Multiple studies show humidity control can decrease virus infectivity and the transmission of diseases like SARS-CoV-2. Controlling relative humidity through humidification systems is necessary for patient health and comfort, and can lower costs by reducing healthcare-associated infections.

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Humidification is health:
why is it worth and how should we
humidify healthcare facilities.
Andrea Oscar Frisiero
October 15th 2020

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What health has to do with
humidity
inside healthcare facilities?

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Healthcare Associated Infections
…are infections people get while they're receiving
health care for another condition.
…happen in any health care facility.
www.health.gov

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HAIs in Europe
https://www.who.int/gpsc/country_work/gpsc_ccisc_fact_sheet_en.pdf?ua=1
• 4,5 million HAI / year, 37k deadly
• 1 out of 18 patients at any given time has an HAI
• Chance to get HAI increase to 1 in 5 in ICUs
• 7 billion € / year
only direct additional costs

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In winter time, relative
humidity falls in heated
indoor spaces.
The capacity of air to contain
humidity increases with
temperature.
Indoor environments are too dry

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Is there a correlation?..
Relative humidity is
THE climatic parameter to
help fighting HAIs!

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Microorganisms
growth
Airborne diffusion
Respiratory tract
infection1 2 3
Infection process
Relative humidity control helps
blocking every step!

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Microorganisms growth1
RH < 80%
Stagnant water is the perfect
habitat for mould and
bacteria colonies.
It’s critical to avoid
condensate formation, both
in ducts and rooms

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2
Pathogens can spread through air
attached to
- Respiratory droplets, emitted by
people while coughing, sneezing,
breathing or talking
- Dust and other particles
Airborne diffusion

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2 Airborne diffusion

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Respiratory tract infection
Mucociliary clearance
• Pathogens and dust particles gets trapped
by a mucous layer which prevents them from
going through the respiratory tract walls
• Continuously moving cilia bring the mucous
flow upwards, back to the mouth
3

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Mucociliary
clearance
UR < 40%
UR > 40%

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Sterling Chart (1985)

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Studies

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Virus infectivity drops when Relative Humidity reaches above 40%.
Noti J.D et al. (2013), High humidity leads to loss of infectious influenza virus from simulated coughs.

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Breathe Easy - Taylor, Stephanie MD. - Sept 2016
“Low indoor air RH was found to be the biggest driver of patient
infections”
10
8
6
4
2
0
12

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Ward MP, Xiao S., Zhang Z., Humidity is a consistent climatic factor contributing to SARS-CoV-2 transmission – Michael P.
Ward et al. March 9, 2020
“Increased relative
humidity was associated
with decreased cases in
both epidemic phases
(c),[…].
Overall, a decrease in
relative humidity of 1%
was associated with an
increase in cases of
7–8%”

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Do we need other reasons to control
relative humidity
in healthcare?

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Electrostatic Discharges (ESD)
ESD can cause damage to costly medical
equipment
The probability of this phenomenon depends on
relative humidity in the environment
RH > 35%

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Comfort
• Climatic factors: temperature, relative humidity,
air velocity, noise, pollutants
• Affects perspiration, eyes and skin dryness,
amount of airborne dust
• Prevent Sick Building Syndrome
Performance
• Increased productivity (+7%)
• Lower absenteeism rate
Wyon P. et al. (2005), “Experimental determination of the limiting criteria for human exposure to low winter humidity indoors”.

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Operathing theater
 T, UR
 VOC, CO2, PM
 Medical gasses
 Pressure
 Bacterical load
Other rooms?
 T
 UR ?
 VOC ?
 CO2 ?
Where do we actually control RH?…

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Wrapping up…

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• Keeping relative humidity between 40% to
60% is necessary for the healing process
of patients, it is an opportunity to decrease
costs and improve performance of healthcare
facilities
• Monitor indoor air conditions in all rooms
• Control RH level with a proper
humidification system

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Thank you for your
attention.