May 12, 2020

Efficiency of disinfection and droplet size

efficiency-of-disinfection-and-droplet-size

With the coronavirus pandemic spreading worldwide, the disinfection business is on the top of online search.

As “The Fog Engineers, we provide the right spraying equipment to efficiently atomize the disinfectant liquid that our customer chooses.

But how do you know which spraying equipment is the best between all the different droplet sizes that can be sprayed?

From Dry Fog to rain droplets, with our atomizing technology we can control a wide range of droplet sizes. Therefore, we’ve conducted an internal analysis to explain the relationship between the efficiency of disinfection and droplet size.

Why a smaller droplet size is more efficient for disinfection?

It all depends on the method of disinfection to fight airborne viruses or surface-adhering viruses.

Infection route

First of all, we need to understand the difference between the transmission of a floating virus and surface-adhering virus.

  • Floating virus: defined as airborne contamination, it happens when someone is sneezing or coughing without covering its mouth. Therefore, the infection occurs while breathing.
  • Surface-adhering virus: defined as cell-to-cell contact infection, it happens when a contaminated object gets in contact with a human body (its hand). If the person touches its face, there can be a mucus infection.

disinfection and droplet size

Surface-adhering viruses have been mainly tackled by the conventional cleaning methods with the task of spraying disinfectant towards objects and wiping off to clean. However, this method has its limit as it requires manpower. There’s also a risk of wetting and damaging electronic objects. And it neither covers spatial disinfection for airborne contamination, nor disinfect all surfaces especially the ones called “negative” as difficult to reach.

To avoid infection via floating viruses, social distance has been implemented in each country (from 1.5 ~ 2 m) to decrease the risk of contamination. However, according to a simulation conducted by the Associate Professor Katsushi Yamakawa of the Kyoto Institute of Technology (Source: Asahi Shimbun), fine particles of 4~8 μm of contaminated droplets were still floating in the air about 20 minutes after the patient coughed without covering its mouth.

Therefore, there is a need to disinfectant not only objects but also the surrounding air in a closed space to efficiently sterilize everything.

Efficiency of disinfection and droplet size

In order to fully disinfect a room and its objects, and simultaneously fight floating and surface-adhering viruses, at IKEUCHI we recommend a more intensive and efficient method by spraying what we call Dry Fog.

What is Dry Fog?

Dry Fog is a fine fog with an average droplet size of 7.5 μm that doesn’t wet the environment and the objects.

Due to its small size, the droplet evaporates in the air before reaching any surface, therefore, not wetting.

We have several successful installations and proven experience in using Dry Fog for humidification purposes in electronics industry, especially in semiconductor fabrication plants and similar production facilities where strict humidification restrictions exist.

IKEUCHI's classification of droplet size

Creating Dry Fog can be done by using a lot of air to break down the water droplets (high pressure systems), but that way is neither economical nor environmentally friendly.

Our AKIJet series and AKIMist® humidifier are the best atomizing technology that can efficiently generate Dry Fog with as little energy as possible.

Why doesn’t a Dry Fog wet?

1) Smaller droplets don’t wet surfaces as they bounce off without breaking.

water-droplet-diameter

Thus, it avoids excessive condensation, wetting and corrosion issues compared to larger droplets.

2) The maximum droplet size our Dry Fog nozzles spray is less than 50 μm.

Our Dry Fog nozzles spray an uniform fog without any large droplets.

For example, other type of humidifier like the ultrasonic humidifier can generate a large amount of small droplets of around 10μm. However, their fog is not uniform in size having larger droplets sprayed at the same time. The inclusion of these large droplets (larger than 50 μm) can wet objects.

droplet size

How efficient is a small droplet for disinfection?

Our patented nozzles AKIJet series and humidifier AKIMist® are characterized by the extremely small and uniform-size spray droplets.

  • Dry Fog droplet size: is on average 10 μm (max. 50 μm)
  • COVID-19 virus: is about 0.1 μm in size and often appears in clusters measuring 5~10 μm

Our Dry Fog sprays a droplet size about the same size of the contaminated droplet floating in the air.

As the diluted disinfectant is sprayed to become the Dry Fog, water in the droplet evaporates quickly leaving the disinfectant liquid to get in contact with the virus and efficiently disinfect.

If the droplets are too big and there’s too much disinfectant liquid, then it becomes corrosive for the spraying unit, the environment with equipment and the human body.

Our Dry Fog sprays a homogeneous distribution of uniform-size disinfectant droplets which allows to envelop and eliminate the airborne viruses.

Dry Fog small droplets

As the floating virus is carried away by saliva, it is believed that, when the face is unprotected by a mask, COVID-19 is propelled through the air in groups of about 40,000 when sneezing, about 3,000 when coughing, and about 600 during 1 minute of normal conversation.

IKEUCHI’s Dry Fog technology can generate about 250,000 fog droplets per second.

This means that roughly our Dry Fog generate 60,000 times more particles than virus-sized droplets.

For contaminated clusters of about 5 μm, if a large amount of Dry Fog of 0 to 20 μm can be generated, it can be said that the probability of contact with the cluster becomes very high.

disinfection and droplet size

Therefore, Dry Fog efficiently spread the disinfectant to get in contact with the virus in the air.

The Dry Fog can saturate a room up to 100% relative humidity (RH) without ventilation. One AKIJet series nozzle (03C type) is suitable for spaces of 100 m3 (without ventilation), covering a distance of 4 m from the nozzle.

For example, to reach 100% RH at 15℃ in a room of 100 m3:

  • From 40% RH to 100% RH: 0.9 L of water is needed to be sprayed.
  • One nozzle of AKIJet series of 03C type (humidifier AE-1(03C)) sprays 2.4 L/hr at 0.3MPa (ca. 3 bar).
  • Therefore, with one AKIJet series nozzle, the relative humidity level will reach 100% in about half an hour.

For an efficient spatial disinfection, please follow the guidelines of fogging time and disinfectant liquid consumption from the chemical liquid provider. 

By increasing the presence of Dry Fog droplets in the air, it sterilizes the air, the walls and the surrounding objects without wetting them (computers, machines, papers, electronics devices, etc.).

At the same time, it is also effective against viruses that have adhered to surfaces, which create the risk of both direct and indirect infection.

Standard virus countermeasures, such as wiping down tables, skin and other surfaces using a cloth soaked in ethanol disinfectant, have the disadvantage of needing manpower, increasing the amount of time and labor required, facing problems with unwiped agents left on surfaces, and being incompatibility with objects such as electronic devices.

On the other hand, without needing operators to control it, using our Dry Fog unit:

  • Reduces the time and labor without needing manpower during the disinfection process;
  • Sterilizes both floating (spatial disinfection) and adhesion viruses in every corner;
  • Efficiently disinfects thanks to the uniform-size of the droplets and the homogeneous spray distribution of disinfectant on all surfaces.

Advantages of Dry Fog for spatial disinfection

  • Cost effective method as no need for manpower (no wiping needed).
  • Used in critical spaces without the presence of operators thanks to the portable format.
  • Highly efficient spraying unit that rapidly and safely deliver an even fog disinfection.
  • Fog sanitation reduce the numbers or airborne micro-organisms.
  • 100% coverage as whole room disinfection allows thorough disinfection of difficult-to-reach places (where sprays and wipes can’t reach), as well as all exposed room surfaces such as ceilings, walls, floors and equipment.
  • Fast spreading of the fog disinfection in a room without wetting.
  • Fog sanitation is a proven method to fight against micro-organisms infections in the food industry for example (Source: Cleanroom Technology).
  • Prevent the risk of cross-contamination with surface-adhering virus and the risk of re-contamination.
  • Safe to use around sensitive electronic equipment thanks to its non-wetting characteristic.

Our disinfection units

For spatial disinfection and contact infection prevention, we offer different type of atomizing technologies.

Have a look to our line-up

We do not provide the disinfectant liquid. Therefore, please follow the guidelines of the disinfectant company in terms of the concentration quantity to dilute and spray, as well as the fogging time and the exposure time for the inactivation of the viruses.

As each country has its own regulation when it comes to disinfection, please respect them.

IKEUCHI fogging unit recognized as an efficient and safe disinfection unit

A study conducted in 2001 with the Osaka University Medical School concluded that IKEUCHI’s atomizing technology is suitable to disinfect ward rooms, operating theaters, and general-use rooms in hospitals.

Thanks to our experience and knowledge, our fogging disinfection unit sprays an even and uniform-size droplet fog, solving major problems hospitals were facing:

  • No danger of harm for workers through contact or inhalation thanks to the complete automation of the fogging process.
  • No damages on the sensitive medical instruments thanks to the non-wetting characteristics.
  • 100% coverage of disinfection from the ceiling to the floor, as well as walls and narrow gaps.
  • Financial benefits with reduction of labor costs due to the simple operation and shorter disinfection time.

Evaluation of an Automatic Fogging Disinfection Unit

A similar study was conducted in 2012 by the Public Health Agency of Canada which concluded that not only our fogging disinfection unit AKIMist®”E” completely inactivate all microbial agents tested, but it is compatible with electronics device. The AKIMist®”E” was used to decontaminate laboratory spaces.

Evaluation of a Dry Fogging System for Laboratory Decontamination

In Slovakia, our Dry Fog AKIMist®”E” is installed in elderly houses, hospitals, stores, offices, etc., as a mobile disinfection unit with the collaboration of RealTime Technologies to fight the spread of the current pandemic (COVID-19).

For more information about their mobile unit, click here

The Slovakian newsmedia MY Žilina covered the successful installation of the mobile disinfection unit.

Click here to read the article

If you have a question about the right spraying solution for your situation, our team of sales engineers is available to help you choose the right product. Please contact them via email.

We are available from Monday to Friday, from 8:30 – 17:00.

Contact us to know more about our products.

Nina Monceaux – IKEUCHI EUROPE B.V.

ikeuchi