humidity to fight flu & influenza viruses

Abstract from ”Influenza and humidity: Why a bit more damp may be good for you!”
by Jane A. Metz, Adam Finn, (Journal of Infection (2015) 71, S54-S58)


Influenza viruses are among the most common causes of human respiratory infections and cause high morbidity and mortality. In a typical endemic season, influenza results in approximately 200,000 hospitalizations and 36,000 deaths in the United States alone.

Relative and absolute humidity


When we consider humidity we generally think in terms of relative humidity (RH); this is the amount of water vapour present in air, expressed as a percentage of the amount needed for saturation at the same temperature. RH affects how hot we feel at a given temperature by altering the effectiveness of sweating as a cooling mechanism. In high RH, sweat does not easily evaporate because the air is already nearly completely saturated with water. Heat is
therefore not lost, leading to continued but ineffective sweating. At cloud level, RH also determines whether it will rain.

Supporting epidemiological data: changes in outside air absolute humidity predict the onset of seasonal influenza epidemics

Shaman et al. studied the correlation between the onset of influenza epidemics and outside air absolute humidity in the United States. First, they correlated the spatial and temporal variation of epidemic influenza onset from 1972 to 2002 (this equates to 1000 different ’flu epidemics in 48 contiguous states) with the concurrently recorded absolute humidity data for these regions.
They demonstrated that negative (i.e. low) anomalous absolute humidity values were typically observed 4 weeks prior to the onset of an influenza epidemic. They found a small (55-60%), but highly statistically significant (p < 0.0005) association between atypically low local daily absolute humidity and the onset of wintertime influenza.
They demonstrated that the model could accurately predict spatial and temporal variations in epidemic influenza. These data were cross-validated by performing 31 year (1972-2002) simulations for each of the 48 states.

Feasible ways of altering indoor humidity

There are data to suggest that outdoor absolute humidity levels affect humidity levels inside and that simple humidifiers may be adequate to raise absolute humidity to levels associated with a significant reduction in influenza virus survival.
Further research into the effects of increasing absolute humidity on influenza virus transmission in humans appears to be warranted. The prospect of reducing influenza associated morbidity and mortality by increasing the absolute humidity in nurseries, classrooms, hospitals, homes for the elderly and general public spaces is an exciting and novel potential strategy for disarming ’flu.

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Do not miss our presentation on Monday, January 14 at 1:45 PM at the Theater A, room C101

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Other products


  • ILS-P and ILS-SO Live steam humidifier.
    with optional High efficiency insulation saving up to 80% condensate losses
  • AEM Evaporative humidifier and cooler.
    Featuring evaporative media that can saves up to 75% in service costs.
  • Dry fog ACA atomizer.
    The best and most economical, static Dry fog atomizer on the market
  • SR – steam ramp.
  • SOS – steamOsorb multi-ramps steam distributor.
  • RH% sensors and controller

IER in the spotlight

The IER electric steam humidifier is an electric resistive steam humidifier that produces pure and sterile steam distributed in a ventilation duct or directly in the room.
Thanks to our patent pending ‘’Guide & Lock’’ system, the removal and cleaning of the stainless steel permanent cylinder is done in minutes without  tools, no electrical connectors to remove, no complicated procedures, no heavy parts to handle or moving parts that can break, and above all: no spare part is required.

The IER humidifier is the best choice for consulting engineers, since its cylinder is equipped with thermal insulation (saving energy) and comes standard with many features that others offer as an option, such as drain cooler,  full modulation, operation and alarm contacts, feedback signal, Modbus RTU, and many more…

 It is also the best choice for mechanical contractors, since it is the most compact electric steam humidifier in the market while offering the easiest access to all components and parts. Installation, set-up and service has never been so easy, you will save time and trouble, your customer will save money and will love you more.

Steam capacity ranges from 6 to 185lb/h, IER is available in voltage ranging from 120Vac/1ph to 480Vac/3ph.

Come meet the fastest growing humidifier manufacturer in North America at boot B4293.


Electrode boiler and resistive type electric steam humidifiers compared


In this article I will explain the difference between electrode boiler and resistive type humidifiers.
They are both producing steam and use electricity as source of energy but they are based on two completely different principles of operation.
Knowing their differences and their limitations will help you to select the best technology for your application.

How electrode boiler humidifiers generate steam?

Electrode boiler humidifier uses electricity flowing through streams of water to create steam. The conductive properties of water are used to carry electric current. The current drawn and therefore steam production relies on water conductivity (typically between 125 and 1250 µS/cm) and also on the water level covering the electrodes surface.





How resistive type humidifier is making steam?

A resistive type (or resistance type) humidifier uses immersed electric heater to heat up the water to the boiling point to produce steam. Current drawn by the humidifier is the result of Ohm’s law; it is constant and only relying on the resistance value of the heater.

Steam output and accuracy

Steam output of electrode boiler humidifier is a direct function of water conductivity and water level. The cleaner and purer the water is, the lower is its conductivity. Water conductivity contained in electrode boiler humidifier cylinder will increase as the humidifier is producing steam. Steam is free of minerals, salts or other substances, so all of those substances stay in the remaining water until a blow down is performed to renew water contents.

Another factor affecting steam output is the amount of scale or lime stone accumulated on the electrodes. Scale is the result of the precipitation of the minerals and salts contained in water. This process is absolutely inevitable for any electrode boiler humidifier as the use of tap water (city water) is required by its principle of operation.


Humidity output accuracy cannot be better than +/-5% RH for electrode boilers, furthermore the steam output will slowly decrease over the operation of the humidifier until the steam output cannot supply the demand. Then the cylinder has to be replaced.

For a resistive type humidifier, steam output is independent from water conductivity (or other conditions), also the possible scale build-up on the heating element will not affect the steam output of the humidifier. Humidity output accuracy for resistive type can be as low as +/-1% RH. This accuracy is maintained over the life of the humidifier.

Water quality

As already mentioned, an electrode boiler needs water conductivity (impurity) to be able to operate, so this type of humidifier cannot accept treated water such as RO or DI water.

Reverse osmosis (RO) is a water purification technology that uses a semi permeable membrane to remove ions, molecules and larger particles from drinking water.
Deionized water (DI), often synonymous with demineralized water, is water that has almost all of its mineral ions removed. Deionization is a chemical process that uses specially manufactured ion-exchange resins.

Resistive type humidifiers can accept very pure water such as RO or DI water. However most manufacturers offering this type of humidifier will use poor materials and/or have limitations due to their water level sensing devices, so they will impose an added cost option for their humidifier able to operate with RO or DI water.

IER humidifier by steamOvap can accept any type of water from tap (city water) to RO water without additional option.


Electrode boiler service consists in removing the ”consumable” plastic cylinder that is not able to produce enough steam anymore by a brand new one.

No recycling program is yet offered by manufacturers for this plastic and electrical spare part that will end in the waste.


In the contrary  steam cylinder of a resistive type humidifier is a pemanent part usually made of stainless steel. When tap water is used, this one needs to be serviced. The service consists in opening the cylinder and removing the accumulated scale inside.

This operation can be labour and time consuming and complicated thus requiring special skills and tools for most of the resistive type humidifiers on the market.

This is not the case with IER humidifier by steamOvap, thanks to its patent pending ‘‘guide & lock’’ system that allows you to open and clean the steam cylinder in a few minutes without needs of tools or special skills.

Cost of ownership

Initial cost to purchase an electrode boiler humidifier is lower than resistive type humidifier.

Most of the humidifier manufacturers are offering both technologies. They price electrode boiler humidifier much lower than their resistive type ones. Their pricing is done the same way printers manufacturers do with ink jet printers versus laser printers. Just like ink jet printers, electrode type humidifiers are cheaper to purchase, but as they will be used and operated the consumables will represent considerable costs:ink cartridges for printers or spare plastic cylinder for electrode boiler humidifiers.

Its low initial costs makes electrode boiler humidifier the contractors choice. Most of the time required future spares are not included in the initial budget. This is a very lucrative business for humidifier manufacturers and one of the reasons electrode boiler humidifier is their entry level product.

IER humidifier price is very competitive; furthermore no spare is required for the service of the humidifier. It is the only humidifier on the market offered with a 3 year warranty.

In any case, total cost of ownership is in favor of resistive type humidifier, after only 18 months in average.


When selecting electric steam humidifier, electrode boiler can be very attractive as promoted by other humidifier manufacturers. Reason is simple: they want your business of spares plastic cylinders for the years to come.

Unless you are not concerned by inaccurate and unstable steam output, plus the cost of spare cylinder replacement over the life of the humidifier and the resulting waste of plastic in the field, then electrode boiler humidifier should be your option.

If you prefer to ensure a good humidity control, save energy by using pure water, as well as lower your environmental impact while optimizing the total costs of ownership for the building owner; then resistive type is the best choice for electric steam humidifier.


3 Reasons to visit us at 2018 AHR Expo

The 2018 AHR Expo will be held Jan. 22-24, 2018 at McCormick Place in Chicago

As a professional in the HVACR industry, there’s no doubt you’ve heard of the AHR Expo, the world’s largest industry event. 

There are plenty of reasons why you should attend the Show in January, but we’ve narrowed it down to the three biggest 😉

Come visit steamOvap at booth 8079

see us at AHR expo

It will be the second participation to the AHR show for steamOvap. If you have missed us last year, you have one more chance to discover our unique and innovative range of humidifiers and controls.

We are dedicated to develop the most sustainable humidification solutions.

Reason #1: IER electric humidifier is the most advanced and sustainable humidifier of its category

IER humidifier by steamOvap is an electric steam generator that uses water immersed resistive heating elements to produce pure and sterile steam that is then distributed in air handling unit or ventilation duct, or directly into space by using our steam distribution box, SB model.
IER humidifier can be supplied with tap or treated water such as softened or reverse osmosis water.
When tap water is used, the scale will comes off the heating elements by the natural contraction and ex-pansion of the tube heaters . scale pieces then ac-cumulate at the bottom of the cylinder without the risk of clogging the drain outlet.
Regular maintenance and cylinder cleaning is very easy thanks to our unique ‘’guide & lock’’ system. It is a safe and proven solution that requires no tool to remove the cylinder and no consumable to be replaced regularly.
Its evaporation cylinder made of stainless steel is covered with thermal insulation in order to reduce energy losses.

Reason #2: Discover our new AEM evaporative humidifier

AEM is an evaporative humidifier and cooler using media is designed to be installed in Air Handling Unit (AHU) or ventilation duct.

Water is circulated in the evaporative media , as hot air is passing through the wet media, water is evaporated by using the latent energy of the air. As a result the air gets cooled off up to 21F (12C) and humidified at the same time.
Evaporation efficiency is a function of the media design and its thickness, higher the surface contact between the air and wetted media is, better the evaporation efficiency is but also higher the pressure drop will be.
Even if it is one of the simplest way to cool and humidify the air this very old technology is being considered as one of the most sustainable ones.

AEM evaporative humidifier and cooler is ideal for installation in AHU with heat recovery heat exchanger:

  • Direct evaporative cooling and humidifying when installed in the supply.
  • Indirect evaporative cooling when installed in the return lowering the air return temperature will result in increased efficiency for the heat exchanger.

Reason #3: Do not miss the world’s first presentation of our new and unique high efficiency steam distribution ramps.

We are proud to present you our solution to dramatically reduce condensate losses in steam distribution ramps.

The high efficiency steam ramps that we have developed use a two layers thermal insulation. this insulation is certified ASTM E84 (equivalent to UL723) and is able to stand very high temperature and fire.

All this at a very affordable cost. 

We will be very happy to show you our demo on our booth.

So come and see us at booth 8079