SAGE Advice on Air Cleaners!

The UK’s Scientific Advisory Group for Emergencies (SAGE) 
​Advice on Virus Air Cleaners

​The UK’s Scientific Advisory Group for Emergencies (SAGE) has produced timely advice on the effectiveness and safety (or otherwise) of air cleaning technologies and devices in the context of fighting COVID-19.

​While the advice focusses on pre-Airora technologies, it is a valuable contribution as it brings together, in one place, the various scientific concerns that older technologies, including HEPA and similar filters, UV-C, Ionisers, PCO and PECO, plasma, electrostatic precipitation, UV-A & UV-B and chemical sprays, are really not up to the job.

SAGE review of pre-Airora technologies

UVA/UVB, ionisation, plasma, electrostatic precipitation and Far UV (222nm)
For these classes of device, SAGE is unequivocal, there is limited evidence of efficacy against the virus and / or significant concerns over toxicological risks during application. At the current time, from lack of detailed evidence (irrespective of the claims of the manufacturers) SAGE does not recommend using these device technologies in occupied rooms.

Fibrous filter based devices (HEPA and similar filters)
The report notes that such devices will remove (but only from the air flowing through the device, not from all of the air in the room) all particulate based contaminants down to ~0.3 micron including dust, soot and microorganisms including in respiratory aerosols.

However, they note potentially severe drawbacks / limitations, including:

• Manufacturers usually rely on claims based on ‘single pass’ effectiveness (i.e., the proportion of pollutants removed as air passes through the filter), which SAGE notes does not represent a ‘real world’ setting. SAGE explains the many real-world variables which together make such single-pass measurements meaningless.
• They don’t remove any gaseous pollutants.
• While high flow rates (CADR) may be required, so as to clean as much air as possible, noise may be a concern with higher flow rate devices. 
• Filters need regular replacement, especially in dirty environments. Poorly maintained filters may produce sensory irritation.
• Higher energy use (thus cost + emissions) than some other systems due to pressure drop over filter. 
• HEPA filter needs to be correctly mounted to avoid bypass.

Enclosed UV-C

• Photoreactivation can occur for bacteria.
• Effectiveness depends on device flow rate, contact time with UV lamps, design and positioning.
• Fan noise may be a concern with higher flow rate devices. 
• Effectiveness may depend on UV lamp quality.

To these points specifically raised by SAGE we would add that:

• High flow rates, which will be necessary in many situations, mitigate against the necessary latency for the UV-C to be effective.

• As for fibrous filters, manufacturers usually rely on claims based on ‘single pass’ effectiveness (i.e. the proportion of pollutants removed as air passes through the device), which does not represent a ‘real world’ setting.

Ionisers

• No evidence specifically against viruses. Evidence for other microorganisms is mixed. A UK healthcare study showed benefits for Acinetobacter infection, but no impact on MRSA and a trial on TB transmission was inconclusive. 
• Most products have little good evidence to support their effectiveness.
• Charged particles can settle on room surfaces rather than being removed, potentially increasing surface contamination.
• Ionisers are affected by environmental conditions.

PCO and PECO catalytic oxidation

• Catalytic oxidation is a surface effect and hence the inactivation needs to take place inside the device.  (i.e. in effect the device acts as a filter, not across the whole room).
• Unlikely to have benefits over UV-C unless there is a requirement to remove other pollutants at the same time. 

To these points specifically raised by SAGE we would add that:

• As with ionisers, PCO / PECO are affected by environmental conditions.
• As SAGE point out, these are in effect enclosed filters, and as such share many of the drawbacks of fibrous filter based devices, including reliance on meaningless ‘single pass’ effectiveness data.

UVA / UVB Lamps

• UVA/UVB lamps in indoor settings will have minimal impacts.
• Potential risks from exposure (e.g., high intensity tanning lights). 

Chemical spray (including bleach based, alcohol based, and glycol based substances dispersed into the air through the ventilation system or a standalone unit.)

• Many of the potential compounds have health impacts and should not be used in occupied spaces for long durations. 
• There is no evidence that triethelyne glycol, or other glycols, are effective against coronaviruses.

The Importance of good ventilation

SAGE, rightly, repeatedly emphasises the importance of good ventilation in dispersing, diluting, and removing airborne (but not surface borne) airborne pathogens.

However, while often beneficial, this is not always either practical nor sufficient, particularly in existing buildings, and so our recommendation is to address shortcomings in ventilation where practicable alongside implementing Airora’s uniquely effective decontamination technology. Indeed, Sage itself suggests that effectiveness of an in-air cleaning device (such as that provided by Airora) can be assigned an equivalent 'air change rate' to be used alongside physical  ventilation.

During the current emergency, building managers have, in response to such advice,  often increased air change rates above those normally required. However, increasing air change rates can also have negative impacts, such as noise, energy cost and emissions and, in some circumstances, drawing in pollution from outside. By employing Airora’s advanced technology, managers will be able to return air change rates from emergency to good levels.

Rating Airora's technology against SAGE’s efficacy and safety criteria

​As can be seen from the above summary, SAGE has little positive to say about pre-Airora air cleaning technologies, limiting their positive recommendations to ‘HEPA and UV-C type filters might help if – see long list of conditions!’.

Given the poor performance of pre-Airora technologies, let us now look at how Airora’s new technology meets those questions that SAGE poses when considering the ability of air cleaners to suppress airborne pathogens safely and effectively within a building:

Is there evidence that Airora is demonstrably effective against SARS-Cov-2?
Airora’s technology has been demonstrated to be highly effective against MS2 Coliphage, an accepted surrogate (as agreed by the CDC & EPA) for SARS-Cov-2. Indeed, the UK HPA Laboratory at Porton Down measured Airora’s technology achieving a Log 6 kill (99.9999%) of high concentration airborne MS2 in under 5 minutes.

Is there multiplicity of relevant, accurate and independent test data as to Airora’s efficacy, both in the laboratory and the ‘real world’?
Yes

Has Airora demonstrated that it does not generate secondary chemical products which lead to health effects such as respiratory or skin irritation?
Yes, uniquely amongst air cleaner technologies, Airora and its expert advisors have identified the entire inventory of secondary chemical products and can confirm that none are known to be hazardous.

Does Airora’s technology create unintended consequences, such as noise, changes in temperature or drafts? No, Airora is not a filter requiring a powerful fan, it disperses its active ingredients gently and quietly.

Can Airora’s technology mitigate short range person-to-person viral transmission?
Given the log 6 reduction of MS-2 achieved in minutes we expect so (and are working on testing to demonstrate this effect).

Is Airora’s technology sensitive to environmental conditions?
No, within normal ranges Airora’s performance is not sensitive to temperature or relative humidity.

Is Airora’s technology sensitive to ventilation rates, room size, room shape, device positioning within the space, air flow within the room etc.?
No, unlike filters of all types, Airora’s technology is not sensitive to air change rates of up to five per hour, an unusually high figure, nor is it sensitive to room shape nor air flow within the room because its active ingredients are not dispersed by air movement but by molecular diffusion. Device position within the space is also not generally critical. Room size is important in that rooms should be no larger, nor smaller, than that indicated in the individual Airora product specification.

Does any ozone produced by Airora remain below 0.2 ppm?
Yes. Airora both produces trace levels and breaks down ozone, preventing its build-up, ensuring that levels remain far below not just the 0.2ppm limit referred to by SAGE, but well below even the tightest regulation and / or recommendations (0.05ppm) worldwide.

Does any formaldehyde produced by Airora remain below 0.2 ppm?
Yes. Airora both produces trace levels and breaks down formaldehyde, preventing its build-up, ensuring that levels remain far below not just the 0.2ppm limit referred to by SAGE, but well below even the tightest regulation and / or recommendations (0.08ppm) worldwide.

Does Airora produce ultra-fine and nano particles?
Yes. Airora both produces and removes (vaporises) ultra-fine and nano particles and testing has shown that there is no build-up of ultra-fines.
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Is there any UV-C ‘seepage’?
Our devices have been tested for UV-C leakage in accordance with BS EN ISO 15858:2016.

As can be seen from the above, Airora’s technology meets all of SAGE’s stated criteria / concerns, and we look forward to SAGE considering our technology when they next update their review!