The Ministry of Education has ordered 2500 carbon dioxide (CO2) monitors for schools but has not yet finalised its order of air purifiers.
The air cleaners are intended to be used in classrooms to purify exhaled air and help lower the risk of Covid transmission in school.
A report to Education Minister Chris Hipkins last month said the ministry intended to place an initial order from overseas before the end of November, pre-empting long freight and possible manufacturing delays, with the intention that they arrive before April 2022.
But the ministry said today it was still "progressing the procurement of air cleaners" and would confirm to the Herald when this had been arranged.
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The ministry has not made public how many devices it plans to order. But it has proposed a mobile fleet of purifiers that could be deployed to schools where most needed - such as immediately after a case was identified.
Education officials are treating vaccination as the first line of defence against transmission of the deadly virus in classrooms, followed by behaviours such as social distancing and masking. Ventilation is next, with mechanical cleaning of the air the last step officials are considering.
Niwa has advised one of the best ways to keep air clean in classrooms is by opening doors and windows to create air flow. Many schools have also adopted practices such as switching classrooms or taking the whole class outdoors to allow stale air to escape - however these practices will become more difficult in winter.
The ministry's report to Hipkins estimated about one in every five teaching spaces did not meet World Health Organisation standards for ventilation. About half of those could easily meet the standard with extra property work and changes in how they are used.
The remainder could require "systemic changes" to be brought up to scratch. While ventilation was the focus, there could be a case for "supplementary air treatment solutions as an extra layer of protection in some cases".
Feedback from schools would help the ministry refine its estimate of how many classes needed work to improve ventilation - but only a handful have raised concerns with the ministry so far.
On December 6, ministry associate deputy secretary Sam Fowler told the Herald in a statement that the ministry was in "the final stages of due diligence" over the air purifiers, with progression based on the findings of a short Niwa study looking at CO2 levels in different classroom types.
The ministry today confirmed procurement was still in progress.
Any school with ventilation concerns was encouraged to get in touch so the ministry could help them over summer.
The ministry did confirm last week it had ordered 2500 portable CO2 monitors, which is slightly fewer than one per school, to be rolled out in term 1 next year. The monitors can be moved to different classrooms where they will be able to identify build-up of CO2 as a proxy for stale air.
Fowler said those would be deployed as part of a "self-assessment toolkit" for schools, which could use them to work out if their classrooms were well ventilated and what they should do to improve. More information would be provided to schools in 2022.
More than 8000 internal environment monitors would also be in schools or being rolled out to them by early next year.
The ministry had also decided against acquiring older purifier units which the Ministry of Health no longer needed, Fowler said.