Wellington's Covid-19 cases are being allowed to exercise in an underground car park, prompting concern that MIQ workers are being put at unnecessary risk.
All of Wellington's confirmed cases of the Delta variant are housed at the Grand Mercure hotel, with the exception of at least one person who is in hospital.
An aerosol chemist says the enclosed air of an underground car park heightens the possibility of transmission, while a public health expert says the hotel does not sound fit to operate as a quarantine facility.
Joint head of managed isolation and quarantine Brigadier Rose King said people staying at the Grand Mercure in Wellington were still able to use the hotel's "fresh air" area - an underground car park.
That is despite having tested positive for Covid-19, and the increased transmissibility of the Delta variant.
"Managed isolation or quarantine is a challenging time that affects people going through it in different ways," King said.
"Being able to have access to fresh air supports their wellbeing.
"Infection Prevention and Control protocols are in place in the fresh air area, and returnees are required to wear the provided medical face masks at all times and to sanitise their hands before and after entering the exercise areas and maintain 2 metres physical distancing from others."
University of Auckland aerosol chemist Dr Joel Rindelaub said he sympathised with those going through quarantine in Wellington.
But he said those measures were not always enough to stop Covid-19, and in particular the Delta variant, from spreading.
"They're definitely helpful, but they're not going to be 100 per cent perfect as we've seen through types of aerosol transmission in the past in MIQ facilities.
"Bringing them along in these hallways or these confined spaces where we know that there isn't the greatest airflow, to a place where they are not regulating the ventilation, we don't know how many air changes per hour are happening in these places, there is a risk for aerosol transmission."
RNZ understands to get to the underground car park people have to leave their rooms and be guided by MIQ staff, generally Defence Force soldiers, to a lift that takes them down to the car park.
Brigadier King said air filtration units had been installed in hallways and lifts, and each room occupied by a positive case had a HEPA only filter installed.
Rindelaub said that was a good standard, but using an underground car park for exercise was still very risky.
"This one cannot even pass the smell test.
"If you are in some of these enclosed car parks you can smell leftover car fumes from people driving through.
"Anytime you're in that environment you know that there isn't enough good ventilation to get fresh airflow in there, so a car park would be much more high risk than an actual outdoor environment where you're getting the fresh air from the environment."
University of Otago public health expert Professor Nick Wilson said he would not want to be anywhere near the underground car park while positive cases were there.
"I don't think it's fair for the MIQ workers to have to be involved in that process because although masks are good, they're not perfect, and so MIQ workers are being unnecessarily exposed to risk."
While filters have been installed in occupied rooms and shared areas, the Grand Mercure is still undergoing ventilation remediation work in parts of the hotel that are in use.
King said that work will be complete early this month, with a second stage of work, on the other side of the hotel which is not currently in use, to begin soon.
The work includes cleaning ventilation ducts, replacing faulty exhaust fans and changing window seals.
Wilson said the Grand Mercure is not fit for purpose, and should not be in use.
"This sounds problematic, I mean the remediation work should have been finished.
"It sounds extremely problematic if people who are known to be positive and infectious are exercising in an underground car park with presumably pretty poor ventilation, so this seems a very unsatisfactory situation."
Wilson said people staying at the Grand Mercure should be provided with exercise equipment, such as exercise bikes, to use in their rooms, rather than being allowed out into the underground car park.
King said the MIQ Technical Advisory Group had calculated the risk of ventilation issues at the facility as low.