Infection prevention
brands support this point. (See table 1) Compared to Brand 2, the Blast air cleaner is: l 412% more cost-effective per m3
/hr.
l 27% cheaper to run. l Top speed noise levels of 43dBA, making it the quietest portable air cleaner in its class.
Air changes and reducing the bioburden The current UK healthcare guidelines from Public Health England (PHE) for new buildings and major refurbishments specify a minimum of 10 ACH (Air Changes per Hour) for treatment rooms. An ‘air change’ occurs when the volume of fresh air delivered is equal to the volume of the room.6 However, as fresh air enters and mixes with ‘contaminated’ air in the room, not all the contaminated air is removed by one air change. One air change removes approximately 63.2% of air contaminants under well-mixed conditions, and a second air change removes about 63.2% of what remains. This means that a room with 10 ACH can take 28 minutes to reduce the starting contaminant concentration by 99%.9
time can be further reduced by increasing the number of air changes. Smart Air recommends delivering the full
10 ACH via portable air cleaners, in addition to air changes from the ventilation system. The
Time to reduce 99% of contaminants ACH
CADR m3/hr
700 600 500 400 300 200 100 0
680
l Unit 3: CADR of 680 m3 changes an hour.
/hr delivers 27 air 450 245
Unit 3 reduces the removal time of 99% airborne contaminants from 28 minutes to 10 minutes just using an air cleaner. If a mechanical ventilation system delivering 10 ACH is added, unit 3 further reduces this time to 7 minutes.9 Portable air cleaners can exceed PHE guidelines, reduce the bioburden, and deliver a constant supply of filtered air. (See Table 2)
10 Unit 1 28 16 Unit 2 17.7 27 Unit 3
Table 2: Effect of air changes on reducing bioburden in a treatment room
more air changes in the room, the faster the bioburden will reduce. The working example above highlights how this works, using the volume of the room and the Clean Air Delivery Rate (CADR) of the air cleaner. In a treatment room of 250m3
, this This
example shows three portable air cleaners running at noise levels of 37-43 dBA making it suitable for continuous operation: l Unit 1: CADR of 245 m3 changes an hour.
/hr delivers 9.8 air
l Unit 2: CADR of 450 m3 changes an hour.
/hr delivers 15.6 air 10
Achieving lower bioaerosols in clinical areas Portable air cleaners have shown considerable promise in reducing airborne aerosols in hospitals. It is the HEPA filters that capture and remove a significant portion of airborne particles from the environment. A study conducted in various hospital wards demonstrated that the use of these reduced the concentration of aerosols by up to 80%.10
This
reduction in airborne contaminants is crucial in preventing nosocomial infections which can prolong patient recovery times and increase hospital stays. In dental clinics, the use of HEPA filters has
also shown promising results in reducing the risk of airborne transmission. A clinical trial focused on the effectiveness of the HEPA units during dental procedures shows a significant reduction in aerosol particles.11
By continuously
filtering the air, the portable air cleaners can reduce the viral load thereby reducing infection and help maintain a cleaner and better environment in the clinic. The study further highlighted that effective
use of air purifiers not only improves the air quality but also reduces the overall carbon footprint in healthcare facilities by minimising the energy consumption related to HVAC systems.
Selecting a portable air cleaner When choosing a portable air cleaner, it is essential to look for the one that delivers the highest Clean Air Delivery Rate (CADR) at the lowest noise level because noise matters. In a healthcare setting where patients need to heal and staff need to work, if the air cleaner is too loud it will be switched off. Look out for marketing tactics that promote
Source: Smart Air UK * Simulations based on typical costs/emissions per unit running on maximum speed, 24/7 for a whole year Table 1
50
www.clinicalservicesjournal.com I October 2024
the CADR on top speed with the lowest noise level. If the CADR and noise isn’t available on all speeds, it is advisable to ask the supplier before purchasing. To operate the air cleaner continuously, check the CADR at noise levels around 40 dBA. It is also important to consider the size of your room and the number of air changes an hour needed to deliver clean air in
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