The advantages of VHP (vapourised hydrogen peroxide) biocides

Recognition of the need to reduce bioburden, or ‘kill bugs’, can be dated back to Dr John Snow in his pioneering work of 1854. What followed was the understanding that certain chemicals, such as formaldehyde, are ‘very efficient bug killers’, and can mitigate the spread of disease.

Unfortunately, however, ‘they are also very good at killing people’, with guidelines being applied in recent years to minimise danger. Here, Howorth Air Technology discusses the advantages of vapourising hydrogen peroxide as a high efficacy biocide.

What is VHP?

Vapourised hydrogen peroxide, or VHP, is hydrogen peroxide that has been evaporated by various means. When pumped into an enclosure so that it micro-condensates to droplet sizes of <5 microns on surfaces, it has very high efficacy for inactivation of bioburden, and can easily achieve 6-log reduction. Although hydrogen peroxide can exist as a gas, it is invariably used in vapour form as a bio-decontaminant; 60% aqueous hydrogen peroxide can be used, but it has been proven that balancing safety with efficacy, using 33-35% aqueous solution, is the preferred option. An added bonus with vapourised hydrogen peroxide is that it is safe to leave any electronic equipment in the enclosure, and indeed it is advised that computers are left running so that hydrogen peroxide can micro-condensate inside and guarantee that all bioburden is inactivated.

Is fogging the same as VHP generation?

The short answer is ‘no’. There is a significant difference in price between a fogger and a vapourised hydrogen peroxide generator, and this is for good reason. The former requires very little hardware to operate, as it is essentially an aerosol spray head. A fogger creates an aerosolised fog of around 5% aqueous hydrogen peroxide solution with large droplet size, which is directional, so will suffer from shadowing. It is also necessary to use additives to stabilise the hydrogen peroxide at 5% concentration, which will be present in the aerosolised biocide, and be ultimately left behind as residue after the biocide has decomposed and evaporated. Typically, silver cations are used to stabilise hydrogen peroxide, but often enhancing biocides such as peracetic acid are also added to the ‘cocktail’, which will leave a toxic residue requiring clean-up. In any case, even with additives, using only 5% hydrogen peroxide and creating a large droplet size aerosol will have limited efficacy, and subsequent inactivation of bioburden to log-6 kill is often difficult to achieve. Any confusion as to whether a generator is a fogger or a VHP system can be resolved by simply looking at the hydrogen peroxide concentration used. If it is less than 10%, the generator is a fogger.


Howorth’s Biogen™ DUO decontamination system incorporates next generation ultrasonication technology. Ultrasonication of hydrogen peroxide to produce its vapourised form offers all the benefits of previous generations of design, but with lower cost of ownership and enhanced long-term performance.

For more information on the Biogen™ DUO system, incorporating next generation, ultrasonication technology, contact Howorth Air Technology.  

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