Wellington, Jan 25 (IANS): As schools across New Zealand are preparing to return for the first term of this year, Education Minister Chris Hipkins on Tuesday announced 5,000 air cleaners have been ordered in an effort to prevent Covid-19 from spreading

"As we know, along with vaccination, testing, good hygiene and physical distancing, good ventilation is important in minimising the risk of airborne transmission of the virus that causes Covid-19," Hipkins said in a statement.

Schools have done a good job keeping fresh air moving through their classrooms, but opening doors and windows to get fresh airflow won't always be practical, Xinhua news agency quoted the Minister as saying.

The first 500 air cleaners are expected to arrive in March and the remaining 4,500 are to be delivered by June and these will be used in targeted areas within some schools in the coming months, he said.

"To help schools identify classrooms and other spaces which get good levels of fresh airflow and those that don't, schools will receive a ventilation self-assessment toolkit with a portable CO2 monitor they can use to help identify areas of concern and the right approaches to improve ventilation."

These 2,500 portable CO2 monitors are in addition to more than 8,000 internal environment monitors which are already in, or will soon be deployed, in schools early this year, he added.

Early observations of a joint study between New Zealand's National Institute of Water and Atmospheric Research and the Ministry of Education support opening windows and doors as the best way to boost the flow of fresh air in classrooms.

The study says that good ventilation removes air from the inside and replaces it with clean air from outside, preventing the build-up of potentially contaminated air. The level of CO2 in a space is a good indicator of the freshness of the air.

"This aligns with the advice and views of international experts -- there is no substitute for fresh air flow," Hipkins said, adding there were also days when opening doors and windows were less effective, when there was no outdoor breeze, or when it rained and schools were not able to open windows and doors as often.

The Ministry is exploring simple systems to assist air quality and natural ventilation in schools, he said.