The places where you breathe the most “countercurrent” from other people


Cram a lot of people into a small space and the CO2 will rise. Buses, trains and ferries scored poorly in RNZ’s tests. The number of passengers made a difference; the lowest reading of 884 ppm was taken on a bus with only five passengers.

The worst RNZ reading recorded, of 5737 ppm, was “absurdly high”, says Rindelaub. This was taken in this double decker bus with standing room.

“It’s ridiculous and it would be a high risk of COVID transmission.”

Masks can reduce the particles you spread into a space and reduce the particles you breathe in. Legally, they must be worn on public transport at the orange level, but transport companies generally do not enforce this rule.

Rindelaub says if he got on a bus he would opt for the best mask possible, like an N95, and wear it properly. Wearing a mask under your nose is “pretty silly”, he says.

“We have decent evidence that Covid is actually attacking you in your nasal passages. That’s where Covid starts infecting you. So if you don’t have it on your nose, you’re not really helping anyone.”

Compared to buses, the highest CO2 reading recorded on a train was 2430ppm over three trips. The highest on a ferry was 1514 ppm taken in a single trip.

Number of readings: 21. Median: 3160 ppm. Percentage of readings above 800 ppm: 100%.

Personal responsibility and public health interventions

On the stand-up bus, my risk of contracting Covid-19 from the soup of particles in the air was reduced by a good quality mask that fitted snugly to my face.

Rindelaub encourages everyone to take personal responsibility and wear the best mask possible to reduce risk.

But he also wants priority given to a longer-term public health measure: better indoor ventilation.

“We spend 90% of our time indoors, whether it’s in the office, at home, in the car or in transport in between. It’s really important to have fresh air all the time. “

He worries even though we now know the dangers of letting breath particles linger indoors, not enough attention is being paid to improving ventilation.

His opinions are echoed by experts in other fields. Dr. Julie Bennett is a senior researcher in the Department of Public Health at the University of Otago.

“I would like to see a ministry or government organization take responsibility for indoor air quality. We have the Ministry of Environment who is responsible for outdoor air quality, but we have no one responsible for indoor air quality.

The Department of Education has guidelines for indoor air quality in learning spaces, and the building code has ventilation standards for new construction. But Bennett says there are no standards or guidelines for existing spaces.

There is certainly no organization walking around with CO2 monitors issuing fines to public spaces with high CO2 levels.

Bennett says an immediate solution is to place prominent carbon dioxide monitors in public spaces.

These can be purchased for around $400.

She says New Zealand is behind countries like France, which has been measuring indoor air quality for several years, and other European countries which have higher building standards than New Zealand.

But our country is not alone in neglecting indoor air quality. Joey Fox, Chair of the Ontario Society of Professional Engineers Indoor Air Quality Group, takes to Twitter to share the importance of ventilation in the fight against Covid-19.

HEPA (high efficiency particulate air) filters are essential in this mission, but their acceptance is uneven across Canada. Fox has been busy battling online misinformation about it. It has also helped to fill a void in specialist knowledge about the operation of ventilation systems in buildings.

Many of his tweets contain complex formulas, but his message is simple. Good ventilation can reduce the transmission of Covid-19 and other diseases.

He already sees a decline in mask use in Canada and doubts that masks alone as a way to reduce Covid-19 are a sustainable public health measure.

“Distancing, lockdowns; those are not practical solutions for the future, but making buildings safe, improving ventilation and filtration everywhere, that’s something we can do,” he says.

He adds that it shouldn’t be up to individuals to bear the burden of filtering every particle of air they breathe so they’re less likely to get sick.

“It is an obligation for society [and] on the building to provide safe spaces for people. »

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