Sharing Ideas

« Back

Humidification: When Knowledge Pays Off


Humidity is often seen under the negative light of mould, uncomfortable conditions, sweat and stickiness. Bad things, in other words, generally considered worth avoiding. On the contrary, in many important cases, humidity is important, if not fundamental.

There are industrial processes where it is needed: for instance, paper printing, wood processing, food preservation. Without diminishing the importance of humidity to industry stakeholders (the majority), however, I should add that humidity is important for people too.

Why is humidity important for human beings?

For comfort? Yes, but temperature usually prevails over humidity.

For health and productivity? Yes! And humidity plays an important role in these cases, perhaps even more than temperature.

How can this be demonstrated and leveraged to increase sales?

We organised a seminar on the importance of a minimum level of humidity in healthcare facilities and pre-school classrooms during the 2019 ASHRAE Winter Conference held in Atlanta on 12-16 Jan, 2019.

Seminar 56, entitled “Humidity IS Health”, explained to an audience of 150+ people the advantages of a minimum level of humidity and the solutions to guarantee this. There were four speakers:

  1. MD Stephanie Taylor, one of ASHRAE’s distinguished lecturers, brilliantly presented her latest findings related to healthcare facilities during her speech entitled “The Effects of Indoor-Air Relative Humidity on Health Outcomes and Cognitive Function in Residents in a Long-term Care Facility”.

    She has always been interested in so-called healthcare acquired illnesses (HAIs) and how to minimise them. In recent years, she has been conducting a study (still ongoing) on how relative humidity influences the infectivity of the influenza virus: surprisingly (and beneficially for us) she has found in undeniable terms that the infectivity of the influenza virus drops when humidity in patients’ rooms is inside the 40-60 %rH range, in actual fact confirming the well-known Sterling chart:

    What’s more, she has also detected an improvement in the cognitive functions of long-term elderly patients when humidity is inside the same range.

    Put simply, a minimum of 40 %rH should always be guaranteed in healthcare facilities.
  2. Alex Generous, from the Mayo Clinic Graduate School of Biomedical Sciences, gave the second speech, entitled “The Impact of Steam Humidification on Influenza Virus in Preschool Classrooms”. This too was very well received by the audience, with Alex reporting that, based on their 1-year study, a significant decrease in Influenza A virus in the air and on the surface of toys as well as less flu-like illnesses among the 3-4-year-old kids was recorded when humidity in the classroom stayed in the range 40-60 %rH.
  3. After these two scientific papers, William Troung and I made some technology-oriented presentations. William explained that high-pressure water atomisers have been allowed to be used in healthcare facilities in the USA ever since Amendment “m” of ASHRAE Standard 170 was published (“New Options! Fogging Systems in Healthcare Applications”); I compared the main steam and adiabatic systems, estimating the running costs of a reference AHU (Air Handling Unit) used in four different North American climates and two different applications (a small office and a large hospital). We were both congratulated, indeed CAREL was in particular, as it seems that we are the first company to have presented a comprehensive and honest comparison between isothermal and adiabatic humidifiers, considering a large set of characteristics that contribute to the running costs of AHUs (energy costs, water costs, pressure drop across the heat exchanger and droplet separators, modulation capabilities of the humidifiers and of all the other devices making up the AHU).

    This picture depicts the CAPEX + OPEX of the 6 humidification technologies that I considered in an imaginary 5000-person hospital in Las Vegas. The lower the segment, the lower the running costs, which leads to the conclusion that high-pressure water atomisers are the most cost-effect solutions for hospitals in the dry climate of Las Vegas, followed by wetted media (they come second because of their higher pressure drop that generates additional energy input for the supply blower).

    If I had to draw a conclusion, I would say that we were able to convince the attendees of the importance of a minimum level of humidity, a subject that is very often refused or neglected, by sharing knowledge that was not available before, i.e. that if humidity is kept in the 40-60 %rH range, patients, the elderly and preschool kids recover and live better.

    And that’s not all. We have also understood that, from a technology point of view, in a world that is rapidly moving towards complexity, comprehensive yet easy-to-understand estimations are fundamental, as well as appreciated, to help users select the best solutions for their needs. And this is true whenever any product/service proposed by a company has effects on the overall system it may be incorporated into, be it an AHU or a supermarket.



Related Posts


Best Defense for Flu Season: The Gorilla in the Room

We will fog you!

Relative humidity: our first ally in the invisible war against bacteria

2018 ASHRAE Winter Conference in Chicago

Kigali, energy efficiency and control schemes - 1st part

Kigali, energy efficiency and control schemes - 2nd part



Trackback URL:

No comments yet. Be the first.