Hypochlorous v HPV: Hypochlorous goes up against HPV in NHS fogging trial



In May 2021 we were given the opportunity to trial the misting of Salvesan hypochlorous within the paediatric ward of a large NHS hospital.

The aim of the project was to measure the effect of misting Salvesan hypochlorous acid on the microbial loading across a range of hand/touch surfaces in previously cleaned and disinfected patient rooms as a direct comparison to HPV.

Two single occupancy patient rooms were chosen. Both rooms were misted with Salvesan hypochlorous acid at the rate of 3ml/m3 but each room was misted with a different machine: room 1 was misted with a new design Aqualution validated fogging machine; Room 2 was misted with a fogging unit sourced by the hospital.



The chosen rooms had been pre-cleaned then disinfected with Actichlor Plus (1000ppm bleach).

Microbial swabs were taken – both ATP for instant measurement and conventional microbiology swabs which were couriered to the lab (One Scientific, Avonmouth) and analysed for aerobic colony counts. Ten swabs were taken in Room 1 and nine in Room 2 before and after fogging with Salvesan. Both rooms were fogged with Salvesan for 4 minutes then left for a 5 minute dwell time prior to taking the post treatment swabs.



Room 1

Results of the conventional microbiology swabs are shown in the table below, expressed as both colony forming units (cfu) per swab and log counts.


 ACC (cfu/swab)Log
Swab sitePrePostPrePostReduction
Bedside cabinet120<10202
Cot bed790<10202
Soap dispenser<10<1000
Glove dispenser<10<1000
Door handle<10<1000
Light switch<10<1000
Bin lid600<10202


The results demonstrate that 60% of the previously cleaned areas tested had a count of <10cfu/swab prior to misting. The areas still harbouring bacterial contamination were the bedside cabinet, the bed rails and the bin lid. Swabs taken after misting show that this contamination has been successfully removed at every sample point.


Room 2

Results of the conventional microbiology are shown in the table below, expressed as both colony forming units (cfu) per swab and log counts.


 ACC (cfu/swab)Log
Swab sitePrePostPrePostReduction
Door handle (internal)21030211
Light switch10<10101
Glove dispenser<10<1000
Soap dispenser<10<1000
Bedside cabinet410<10202
Phone headset<10<1000
Bed rail2270<10303
Spine of folder at end of bed270040312


The results demonstrate that a third of the areas tested prior to fogging had a count of <10cfu/swab. The areas still harbouring bacterial contamination were the door handle, light switch, bedside cabinet, chair, bed rail and folder. Swabs taken after misting show that two thirds of the areas were very clean with the remaining three showing very low levels of contamination. The most contaminated two areas were the bed rail and the spine of the patient folder. Misting successfully removed 99 – 99.9% (2 – 3 logs) of the bacteria present in these areas.



The rooms had been cleaned prior to the fogging trial using a spray and wipe rechnique. However, our swabbing showed that over half of areas sampled (10/19 areas) still had microbial counts of >10cfu/swab. After misting with Salvesan the number of sites with contamination present in excess of 10cfu/swab was 3/19 (~15%). The total number of bacteria enumerated was 7340 cfu in the 19 pre samples and 90 cfu in the 19 post misting samples. This is a 2 log reduction (99%) in a previously cleaned and sanitised area. Misting with Salvesan confers consistent benefits when used in addition to traditional hygiene measures. Other projects have demonstrated that the make of fogger also has an impact on the effectiveness of the fogging process.


Click here for the full lab report.