Decontamination effectiveness of Hydrogen Peroxide vs UV Light


At a time when infection control is at the forefront of everyone’s thoughts, it is worth considering that not all decontamination is created equally. How clean is clean anyway?

There are a lot of tools and technologies available to us to decontaminate clinical areas and patient treatment rooms. Different rooms have different requirements. An operating theatre needs a different level of cleanliness than the waiting room for example. And therefore, we need to think about using the right decontamination technology for the right purpose.

How do we measure cleanliness anyway? We need to think specifically about infectious agents, whether they be virus particles or bacteria, the bioburden of a particular space. To what degree can we decrease that bioburden? How far can we drive back those infectious agents?

We are all familiar with the claims of well known brands of household bleach. They kill 99.9% of all known germs. Have you ever considered what that actually means? It does not mean that there are 1000 known germs and this bleach can kill 999 of them outright but the last known germ is going to stubbornly refuse to die whatever we do. It means that if we started with 1,000,000 germs of any sort (bacteria or virus particles for example) on a surface, then once we had cleaned that surface with our household bleach there would be 1000 germs left. That’s not too bad for our homes. But we probably should expect more in healthcare settings where our loved ones are being treated for potentially life threatening conditions.

So, a 99.9% (also known as a 3-log) kill is what we can buy off the shelf in the supermarket. What other options are open to us?

There has been a lot of interest in UV decontamination over the last few years. And it’s appeal is obvious. UV light can destroy harmful bacteria and virus’ and leaves no residue to clean up. Seems perfect, right? There are a few problems though.

UV radiation is light. Wherever you get light you get shadow. The shadow is the place the light can’t get to. Guess where our infectious agents are going to continue to thrive? To continue to pose a threat to us, our patients, our loved ones. Because the UV radiation cannot get into every area of a room it cannot do its job and destroy bacteria and virus in every area of a room. Clinical areas can be complex spaces with equipment and instruments and computers and cables, a lot of objects that can cast a shadow.

The other issue with UV is that its efficacy (how successfully it can kill these pesky infectious agents) falls away the further you get from the source of the light. UV radiation is governed by the inverse square law. In short, a bacteria 1cm from the light source will be subjected to 4 times more radiation than the same bacteria 2cm from the same source, 9 times more than the bacteria 3cm away.

To get around these problems people have tried to make mobile systems that can be moved around a clinical space, even mounting UV lamps on robotic bases. With these innovations a UV system can achieve a 99.99% or 4-log kill rate. From our original 1,000,000 infectious agents we now have only 100 left, 10 fold better than our household bleach. But that 99.99% kill rate probably isn’t distributed evenly throughout a room. There will still be infectious agents in the hard to reach places, still lurking in the shadows. How sure can we be that the UV radiation could get behind the door handle?

Hydrogen peroxide is a hugely successful biocide. When 30-35% hydrogen peroxide is deployed in a space as a vapour it can achieve a 99.9999% kill, a 6-log reduction in the bioburden of the room being treated. Remember those 1,000,000 infectious agents we have been concerned with? Hydrogen peroxide would leave us with just 1. Hydrogen peroxide has the added benefit that it leaves no harmful residue. It breaks down naturally to water and Oxygen, so there is nothing to fear or to clean up once it has done its job.

One of the problems with hydrogen peroxide vapour has traditionally been the time it takes to fill a room with the vapour. It could take hours, depending on the size of the room. You would then need to allow for dwell time, to allow the hydrogen peroxide to do its work. And then you would need to aerate the room; remove any unused hydrogen peroxide and make the room safe for people to use again.

Howorth Air Tech’s BioGen Duo has revolutionised this type of decontamination. The BioGen Duo generates its vapour through ultrasonication. This means it can fill a room with vapour in minutes rather than hours. It also has an aeration system. These innovations mean that Howorth has reduced the time it takes to thoroughly and repeatably decontaminate a room with hydrogen peroxide from a full day to a couple of hours.

Decontamination with hydrogen peroxide and Howorth’s BioGen Duo is 1000-fold more effective than household bleach and 100-fold more effective than even the best UV system. And unlike UV it is not affected by shadowing and can get to all areas of a room by virtue of being a vapour. At a time when we are trying to protect the most vulnerable members of our society from viral infection or subsequent secondary bacterial infection, BioGen Duo is the obvious answer.

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