AIRBORNE INFECTION CONTROL


beginning with the launch of the peer- reviewed A Healthcare Engineering Roadmap For Delivering Net Zero Carbon document, co-produced with HEFMA and the Carbon and Energy Fund, and available to NHS organisations to download via the Carbon and Energy Fund website, and to members of IHEEM, IFHE-EU, and HEFMA via their respective websites, from 1 March. A ‘follow-up’ webinar on 14 April would, he said, include ‘a fantastic line-up of speakers’.


Launch of Workforce Strategy On 12 March, meanwhile. IHEEM and HEFMA would be launching a joint Workforce Strategy, again followed up with a dedicated webinar, in May, linked to a number of initiatives the Institute had planned– ‘especially around IHEEM national programmes on apprenticeships’. Then, on 16 March, IHEEM would be holding a whole-day joint event with NHS England, where speakers would include Pete Sellars, Simon Corben from NHSE/NHSI, a Minister, and other senior personnel from NHS England. Pete Sellars closed by thanking all members of the profession for their ‘massive help and support’ over the previous 12 months. As a final aside, he said that since the activation of the ‘new’ IHEEM website, the Institute had – over a 10-11 week period – received over 200 requests from individuals wishing to join, in contrast to a ‘normal’ rate of perhaps 5-6 requests per month; ‘fantastic news’ that many people were recognising the benefits of what IHEEM was striving to do as a professional body to support healthcare estates and healthcare engineering personnel throughout their careers. He closed by asking all attendees that where there was an opportunity to let their staff, such as tradespeople and apprentices – who might not normally engage with the Institute – to do so, via educational events such as this, they should; many would find the content extremely valuable.


A focus on air-cleaning devices Cath Noakes then began her presentation, explaining that – with considerable current interest in the subject, she intended focusing principally on air cleaning devices. However, she would, she said, start by discussing SARS-CoV-2, the virus responsible for COVID-19 transmission. Showing her first slide, she said: “This slide should hopefully illustrate some of the complexity around the virus’s transmission – about which we have learned quite a lot over the past year. We initially focused, this time last year, on transmission through droplets, and concern over surfaces, with a major focus on handwashing and surface cleaning. Over the past year, however, we have discovered more about the coronavirus; being a respiratory virus, it’s contained


26 Health Estate Journal April 2021


Start at the top of the Hierarchy of controls and identify possible control measures within a category before moving down to the next category in the hierarchy


Elimination


Controls higher in the hierarchy are more


effective than those lower in the hierarchy


Engineering Controls


Controls should be practical to be implemented, and ideally to be maintained


Care is needed to not transfer risks or introduce new risks when considering controls


Administrative Controls


PPE Substitution


Some simple examples


Stop a work activity if it is not considered essential


Work at home; Use of alternative transport to get to work


Use of screens and barriers; Automatic doors


Spacing marked out on floor; Cleaning regimes; Signage to encourage behaviours


Gloves; Facemasks


The use of multiple different independent controls gives defence in depth through different layers of protection


Figure 2: The HSE's Hierarchy of Risk Controls.


within people’s exhaled breath. There is growing evidence that as well as these large droplets, you can also transmit it through aerosols, including some smaller ones, that can stay in the air for long periods. Although they don’t seem to transit through the whole of a building’s HVAC system, they certainly pose a risk to somebody sharing a room with others.” (Fig 1).


As more information on the virus had emerged, the importance of both ventilation and airborne controls had assumed greater prominence – something which applied equally to ‘multiple other diseases’. Thinking about transmission, Prof Noakes explained that when somebody exhales – this might be simply through breathing, although more particles were generated during talking, coughing, or sneezing – they produced a cloud of droplets and aerosols ranging


Fate of droplets and aerosols


50 45 40 35 30 25 20 15 10 5 0


0 10 20 30 0.25


from under one micron to up to 1000 μm in size. The tiniest were more numerous than the larger ones, but probably carried less virus. The Professor said: “When you are very close to somebody, you can be exposed to the large droplets – hitting you in the eye or nose, to medium-sized particles – which you may inhale into your mouth, and to the tiniest ones – potentially inhaled into your lungs. However, an individual further away is only exposed to the droplets that can stay in the air the longest.”


Controls via engineering design From an engineering perspective, the Professor said healthcare engineering professionals should be thinking about the controls they could put in via engineering design. She hoped they were already considering how they applied the HSE's Hierarchy of Risk Controls (Fig 2)


0.20


0.15


0.10 3 min 0.05 30 s 0 40 50 60 Diameter (μm) Figure 3: Size of droplets and aerosols and relative time to fall. 70 80 90 100


Falling velocity (m/s)


Time to fall 2 m (min)


©Professor Cath Noakes, University of Leeds


©Ron McBeth, Health & Safety Executive


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