Business editor Nikki Mandow argues the case of a vaccinated, mask-wearing, plane cleaner contracting Covid-19 should be setting off company alarm bells around their legal duty to provide adequate PPE.

Bear with me, but I’m going to begin with the Swiss cheese model of Covid-19 protection. It’s been around a while but it was new to me when a book club friend sent this powerful BBC visualisation to me last week. 

Suddenly it provided a clear explanation to the seeming mystery of how a worker cleaning a plane that had recently arrived from Ethiopia with an infected passenger on board contracted Covid-19 despite being fully vaccinated and wearing the PPE he had been given. 

The “Swiss cheese respiratory pandemic defence model” was first created by Ian Mackay, a virologist at the University of Queensland, Australia. 

Imagine a block of Swiss cheese with its characteristic holes, sliced into nine pieces. Each layer represents one of our defences against the virus.

Source: Michelle Roberts and the BBC Visual Journalism Team. Reproduced with thanks

The visualisation then goes through the nine things that put together should protect a population against Covid-19. Some of them, like testing, contract tracing and ‘stay home when sick’, are more about protecting the rest of us from infection arising (in the case of New Zealand) from the border. 

But others are super-relevant to protecting New Zealand frontline staff – health, airport and MIQ workers – as they go about their jobs. 

Number one protection is vaccines, the model says. Vaccines are powerful, but as we know from the plane cleaner, not 100 percent effective.

Then there’s social distancing. But again, as was proved from several cases in MIQ and now the plane cleaner, it’s possible to catch the virus without even being in the same room as an infected person. Airborne virus particles can linger.

There’s fresh air and good ventilation. Those are things companies need to be vigilant about in terms of keeping staff safe. Why did it take the Pullman Hotel outbreak at the end of January for any action to be taken on hotel ventilation systems – despite that potential problem being raised with Ministry of Health officials back in September or October last year? And knowing about airborne transmission, why was the air conditioning turned off in a “red-zoned” plane being cleaned?

Washing hands and disinfecting surfaces is important, the Swiss cheese science model says – that’s why the cleaners were in the plane in the first place. “Good hygiene can help stop the spread of the virus,” the model says, “but the risk from particles in the air remains”.

Finally, critically, there is the importance of wearing a high-quality protective mask.

Source: Michelle Roberts and the BBC Visual Journalism Team. Reproduced with thanks

“Even the highest-grade masks still let some virus through.” And frontline workers – at least ones outside of hospitals – are not being given high grade masks. They are being given surgical masks.

Surgical masks don’t provide high-quality protection

Newsroom has been writing for more than a year about the dangers arising from inadequate mask protection for workers around Covid. First it was home care and other community workers not getting masks at all, The Government and employers finally fixed that – kind of – giving out surgical masks.

But more recently we’ve been concerned that employers of border and other front line workers at high risk of being exposed to Covid are being given those same ill-fitting, lower-protection surgical masks, rather than the recommended higher-protection, tightly-fitting P2 or N95 masks. (P2 and N95 are to all extents interchangeable in terms of level of protection – pretty much just different country standards.)

On April 16, Newsroom published a story revealing that even though wearing a P2 or N95 respirator mask is apparently mandated for staff at the airport and potentially for aviation security staff now working at isolation and quarantine facilities, these at-risk workers are being given surgical masks instead.

The graphic below is from an information poster for staff used by Aviation Security and the Civil Aviation Authority. The comments in red are ours, not theirs. But basically, it appears the masks issued for workers – including the one used in almost all cases, the surgical mask – do not meet even the employer’s own guidelines.

Source: “Face masks simple poster and FAQs”, CAA and Avsec, December 2020

A Civil Aviation Authority spokesperson told Newsroom that on-airport staff in Auckland would move into a ‘green zone’ or ‘red zone’ model when trans-Tasman quarantine-free travel started on April 19, with staff in the ‘red zone’ using additional PPE including gowns, masks that meet N95 filtration standards and face shields. 

Newsroom was not able to confirm whether that has happened.

Surgical versus N95 masks

Trying to work out how different masks compare with each other in terms of protecting against Covid-19 is a bit complicated. 

Still, some searching came up with this unequivocal graphic from the US Centre for Disease Control.

Source: US Centre for Disease Control 

As the CDC makes clear, surgical masks, which MIQ and airport staff are provided with, “do NOT provide the wearer with reliable protection from inhaling smaller airborne particles”.

So why the confusion?

It may be around the fact a 95 percent figure is used when assessing both surgical and N95/P2 respirator masks. It’s just not the same 95 percent.

Newsroom came across this explanation in a myth-busting newsletter from the $US10 billion global healthcare supply chain company Owens and Minor.  

“Myth 4: Surgical and respirator masks offering a BFE [Bacterial & Viral Filtration Efficiency] of 95 percent provide the same level of protection.


The way in which the two tests are performed between respirator and surgical masks, means that they are not measuring the same thing, the newsletter says.

“[With a surgical mask] you’re not getting even close to the same level of protection that an N95 mask will provide.”

“Bacterial filtration efficiency (BFE) used to measure surgical masks, is measuring 3 microns particles at a fairly low flow rate. 

“The respirator test measures 0.3 microns (smaller) particles at a much higher flow rate, so it is more stringent than the surgical mask test. 

“A common error is when people compare a 95% BFE mask to an N95 respirator, they think they are getting the same filtration and will go with the easier to breathe mask.”

And here’s the scary bit: “If you take a 95 percent BFE [surgical] mask and run through the same test used to measure an N95 filtration mask, it will usually only achieve a 40-60 percent efficiency, so you’re not getting even close to the same level of protection that an N95 mask will provide.”

In Turkey, airport security staff wear masks and face shields. In New Zealand they have been making do with surgical masks. Photo: Getty Images

What this appears to suggest is airport and MIQ staff are being provided by their employers with masks which provide only 40-60 percent of the protection they would get if they wore ones that actually matched the standard those same employers are ostensibly meant to be meeting.

One further complication: N95 respirators are basically designed for men working in industry – construction workers dealing with dust, for example. They aren’t made for nurses and cleaners, not if they are women, anyway. 

A 2020 study by the University of Western Australia found that N95 respirators fit only 85 percent of women and that dropped to 60 percent for Asian women.

Everyone agrees wearing ill-fitting masks reduces the level of protection. 

So what are the implications for employers? 

Simon Auty is a theatre nurse and a board member of the New Zealand Nurses Organisation. While he is mainly advocating on behalf of medical staff, he says the principles around best practice with mask protection apply equally to people working at MIQ and the airport. 

At the very least, he says, employers should see the provision of the right masks for their staff as a health and safety at work issue – with the incumbent duty of care, and the incumbent penalties that go with failure to mitigate any other potential hazard at work.

According to the law, PPE must be provided by the employer and must be suitable for the nature of the work and any risks associated with the work. It must be a suitable size and fit and reasonably comfortable.

The key phrase in there is “properly fitting”, Auty says. “The ‘one size fits all’ approach to PPE provision means that a significant proportion of the healthcare workforce will not be protected because the provided equipment does not fit – remember the employer is obligated under law to provide properly-fitting PPE.”

Get it wrong under the act and fines can be hundreds of thousands or even millions of dollars, and possibly involve going to jail, as this article from law firm Harkness Henry sets out. 

Auty argues – strongly – that nursing staff in New Zealand should be wearing masks with even higher protection than N95/P2 when they are dealing with patients who have, or potentially have Covid-19, in line with demands for 99 percent filtration coming from nurses in the UK and Germany

Auty isn’t the only person not surprised the vaccinated, mask-wearing plane cleaner caught Covid. Companies or government agencies employing staff wearing only surgical masks might want to take more notice of that Swiss cheese.

Nikki Mandow was Newsroom's business editor and the 2021 Voyager Media Awards Business Journalist of the Year @NikkiMandow.

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