Introduction to the new disinfecting technologies
Technology 1:
Advanced Photocatalytic Oxidation (APO) This product is primarily used for active reduction in live microbial activity in the air. It filters the air, whilst also producing and circulating a hydroxyl radical (free radical) anti-microbial aerosol. Before the introduction of this patented technology, for free radicals to effectively kill microbes in the air and on surfaces, the concentration used would have to be above the safe maximum exposure levels (MELs). This would mean that either significant personal protective equipment (PPE) needed to be worn in the rooms during treatment, or the room would need to be vacated. The manufacturers of the new APO products used in the study, have discovered a method of reducing the concentration to well below safe MEL, whilst maintaining therapeutic value. This is achieved by reducing the concentration of free radicals, then passing it over titanium dioxide in the presence of UVc light.
There was at the time of testing some unpublished evidence, that this technology has the secondary effect of reducing live microbial levels on surfaces. That evidence was published in this journal in December of 2024.12
Technology 2:
Photocatalytic solution (PS) This surface treatment uses similar photocatalytic technology to the APO product, in that it uses a form of free radical as its active antimicrobial. As a persistent surface treatment, it is applied every three to six months to clean surfaces, remaining in place until worn away through everyday use. Like any persistent antimicrobial technology, the reapplication schedule is based on the perceived levels of use of the surfaces and may change from surface to surface. At the time of testing, a test is being developed that will show the presence of sufficient antimicrobial to remain therapeutic. With both technologies, manufacturers
recommend that routine standard cleaning should be continued.
Study design/methodology Ten rooms across a range of classrooms and social interaction areas (including three classrooms to be used in a sub- sectional study) were selected to be studied over a 12-month period. Two surfaces were selected in every room, with swabs taken from 20cm2
areas for both
BSRMA and culture (740 in total for each test). 20 x air sampling measurements
INFECTION PREVENTION As we don’t routinely test surfaces, there has
never been an agreement to produce acceptable standards for what would be deemed to be ‘safe’ levels of contamination on surfaces in hospitals
were also taken, at 20cm above each area (8,400 samples in total). A control room was selected, and all rooms were tested pre any interventions or treatments. The control room continued with the University standard cleaning regime and products. Tests were then conducted at approximately the same time of day, on the same day of the week at four to six weeks, and at 10 weeks post intervention. The multi particle sampler unit used
for air sampling, can determine six different particle sizes in any one sample. One litre of air is sucked into the unit over one minute. Particles are measured in their respective size groups, and a digital read out is taken of each particle size. In all rooms, surface and air samples
were taken at the same sites at every visit. Samples were taken between 6.30 am and 7.30 am in all rooms. These times are approximately one hour after the standard cleaning has been completed, and before the rooms began their normal daily routine work. Up to 15 people used these classrooms at any one time. Normal study classes and meetings continued to take place throughout the testing period. The sub section of this study is the part of the study that is reported here in Tables 1 to 3. The sub-sectional study was also designed to use the same test methods over a 10-week period, to test the efficacy of the two new technologies
described above. The total number of samples in the sub-sectional study was 48 x BSRMA counts and 48 x bacterial species identification cultures, (no viruses or fungi were able to be cultured). Whilst it is agreed APCs are not an exact measure, highly accurate particle size counts are an acceptable method of determining air particle counts by size of particle for bacteria, viral units and fungi (see Table 4). It is therefore also possible to determine that increases or reductions in particles of certain sizes would lead to the conclusion that these equate to increases or reductions, at least in part, in bacterial species, viral units and fungi in the air.8,11,13 The study was blinded to all staff
except the cleaning supervisors, who were instructed not to intervene in any cleaning within the rooms to be tested. Rooms of equivalent size with similar
footfall, sharing the same ventilation system, were selected. One classroom was used as the control, a second room was treated with both the two new disinfecting technologies already described. Room three had APO only and room four had PS only. The rooms were in use for all except two weeks of the 10-week period. The normal surface cleaning regime was continued in both rooms by the same cleaning operatives, using identical disinfecting/decontaminating chemicals and equipment.
There are no international standards or even national standards, recommending which surfaces in hospitals should be sampled for bioburden, how often, and what test methodologies should be used.7
April 2026
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