The rules for mask wearing is about to change and things like a bandana or t-shirt across the face will no longer count as a mask.

Prime Minister Jacinda Ardern said under the red setting, masks must now be worn at food and drink businesses, close proximity businesses, events and gatherings. The same exceptions for when people are eating, drinking or exercising still apply.

Workers mandated to be vaccinated will have to wear a medical grade mask when working in public-facing roles, which includes blue medical grade masks.

University of Canterbury associate professor of epidemiology Arindam Basu says this is a welcomed move.

"The thing that will need to go with it is that there needs to be a bit more education and instruction ... in how to wear the mask."

A mask that is tightly fitted to the face is better than a cloth mask, he said.

University of Otago Wellington senior public health researcher Dr Lucy Telfar-Barnard said N95 and P2 were the best options because blue surgical masks were more likely to have leakage around the edges.

"I absolutely recommend them, if people are able to access them. I know that they're in short supply at the moment."

In the meantime, there are various ways of improving the fit of a blue surgical mask, Telfar-Barnard said.

"If you've got a lightweight cloth mask that fits you well you can wear that over the top, or you can use that blue mask cut down to use as a filter in a filter pocket in a cloth mask that fits well.

"You can use a mask brace - there are various arrangements of elastic bands or cut silicon that you can fit over your head. That will hold that close to the face and create that seal all around the cheeks and chin, as well as using the nose wire to make sure it fits well around the nose."

Even a well fitting cloth mask on its own is better than nothing at all, she said.

Masks in schools

School teachers across New Zealand will now have to wear medical-grade masks.

Auckland Primary Principals' Association President Stephen Lethbridge says he'd be lying if he said he wouldn't have been happier with N95 masks.

The ministry has secured a supply chain for appropriate masks for teachers and school workers. Lethbridge says they're hoping to have these before term one starts.

Some schools have been proactive in securing N95 masks, he said, but they're really hard to find.

Teachers and children from year 4 and up will now be required to wear masks in schools.

Individual schools will decide whether teachers of younger students will wear them, Lethbridge said.

"A number of schools are suggesting and probably putting into their health and safety practices that all the adults on site will wear masks."

Finding masks small enough for children is a challenge but Lethbridge says they adapt to wearing them.

"Never underestimate a child's ability to do the right thing," he said.

Schools have been designing ways for children to get a break from wearing them throughout the day.

Many schools will provide a mask if a child turns up without one, he said.

Advice for people who wear the niqab

It is unclear what the new rules mean for women who wear a veil - or niqab - covering their nose and mouths for religious reasons.

Islamic Women's Council national coordinator Aliya Danzeisen says the rules won't impede the community at all and the only issue will be people verifying it's being worn.

People who wear a veil can wear a mask by sliding it onto their ears and wearing it underneath their veil, she said.

"It shouldn't prohibit anyone or cause any difficulties with someone applying the mask. Malaysia's being doing it now for over year and they haven't had any difficulties with it at all."

It isn't appropriate for someone to ask someone wearing a veil to lift or remove it in any way, but Danzeisen says a woman can press near her nose to show the outline of the mask underneath.

"There isn't anything that's revealed regarding the person's beauty and therefore people who wear the veil feel they shouldn't show it to other people who are not within their family."

The council says people need to be proactive in expressing their needs.

Danzeisen advises that women wearing a veil ask that another woman interacts with them if needed.

"For women who wear it, it's a very important thing so people who are asking people who wear it - be respectful, we can accommodate and make it work for everyone."

The council will provide advice to anyone who raises concerns with them, she said.