INFECTION PREVENTION 100 100 95 95 100 90 90 95 85 85 90 80 80 85 75 75 12 hours 80 Air cleaning tech Fig 1. Percentage reduction in surface CFU counts (pcm2
(VOCs) and CO2. It is therefore not an exact science to measure particles and relate the results to viral units, bacterial CFUs or fungi alone. It is however, not unreasonable to determine that an overall reduction in particle counts would indicate a safer environment in which to breathe.8
75 It is also not unreasonable
for us to extrapolate that the smaller particle sizes are most likely to contain the majority of viral units (0.1 microns), the mid-size to contain bacterial CFUs (1 micron) and the fungi to be the largest size particles (5 microns).8 The new technologies introduced together in the previous paper3 used in this study were:
and then
n Technology 1: Advanced Photocatalytic Oxidation (APO) This technology is primarily used for active reduction in live microbial activity in the air, however, the manufacturer claims it also has an effect on surfaces. It works by filtering the air, whilst also producing and circulating a hydroxyl radical (free radical) anti-microbial aerosol.
n Technology 2: Photocatalytic solution (PS)
This surface treatment uses similar photocatalytic technology to technology 1, in that it uses a form of free radical as its active antimicrobial. As a persistent surface treatment, it is claimed to last for six months on surfaces subjected to high levels of frictional forces, and up to a year
).
on surfaces that are not subject to this type of wear. A more in-depth introduction to these technologies is included in the previously referenced paper.3
It is worth noting at
this point, that both manufacturers and the most up-to-date technical standards, recommend routine standard cleaning is continued when persistent disinfection techniques are used.9
Study design and methodology Two offices of equivalent size with similar footfall, sharing the same ventilation system, were selected. The first office was treated using the air handling technology (technology 1) and the second office with the persistent surface treatment (technology 2).
A single air cleansing unit was placed close to the main entrance door of the first room and a single coating of the persistent disinfectant was applied using a fine mist spray gun in the second room. Surface samples were taken using sterile Dacron swabs, dampened with Aespetol (New Horizons Diagnostics Baltimore USA). In both rooms, surface samples were taken from an area of 20cm2
on flat tabletop surfaces made of similar materials, allowing for maximum potential to gain a result. Evidence in previous studies has shown that on surfaces where BSRMA shows live CFU counts are low, culture rarely produces a result.10-12
Samples were tested using the Profile 1 BSRMA test for live CFU
The air particle counts at all particle sizes in both rooms reduced at every test point over the 36 hours. Of particular note is the reduction of particles in the size range most likely to include airborne viruses
42 24 hours Disinfecting tech 36 hours
numbers, and also blood agar plate culture for pathogen identification. In both rooms, surface samples
were taken at two sites, as far apart as possible. One sample was taken from a tabletop at the front of the room near the main entrance, and the second from a tabletop towards the rear of the room. The first samples were taken in both rooms after standard cleaning and before the new technologies were applied. The rooms began their normal daily use at approximately 7am. Up to 10 people were in both rooms at any one time, whilst normal meetings and work routines took place. The second samples of the day were taken at the end of the working day, after the occupants had left and before standard cleaning could take place, at approximately 7pm. In both rooms, air particle counts were taken at the same time using a Met One particle analyser. This analyser uses lasers to differentiate between particles of 0.1, 0.5, 1, 2, 5 and 10 microns in size and is considered to be accurate and has the advantage of being easily portable.9
All
air particle samples were taken at 3m, and 10m distance from the main entrance door.
Results/data n Day 1. BSRMA results in the trial room
using technology 1 (air cleaning unit), showed that live CFU surface counts taken from close to the main entrance door reduced from 246.97 CFU pcm2 at 7am, to 29.09 CFU pcm2
at 7pm, a
reduction of 88.22%. At the back of the room, CFU surface counts were reduced from 196.57 CFU pcm2 34.19 CFU pcm2
at 7am, to at 7pm, a reduction of
82.61% after 12 hours. In the trial room using technology 2 (persistent disinfectant), live CFU surface counts taken from close to the entrance door reduced from 291.96 CFU pcm2 at 7am, to 1.21 CFU pcm2
at 7pm, a
reduction of over 99.59%. At the back of the room, CFU counts were reduced from 246.82 CFU pcm2 0.78 CFU pcm2
at 7am to at 7pm, a reduction of over 99.69% after 12 hours.
n Day 2. In the trial room using technology 1, live CFU surface counts from close to the entrance door decreased overnight from 29.09 CFU pcm2 CFU pcm2
at 7pm, to 3.57 at 7am. This equates to a
further reduction in CFUs of 87.73% and a total reduction over 24 hours of 98.56%. This count remained low at 7pm at 3.75 CFU pcm2
, a total reduction over
36 hours of 98.48%. At the back of the room, CFU surface counts were reduced overnight from 34.19 CFU pcm2
to DECEMBER 2024
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