The three MPs who have an exemption from wearing facemasks are all from the same small Act Party.
In an unusual coincidence, Karen Chhour, Simon Court and James McDowall are all members of the 10-member Act caucus and are the only MPs who are exempt.
Speaker Trevor Mallard said he was satisfied the exemptions were justified.
Act leader David Seymour said each MP had a distinct reason for an exemption and each supported Act's policy that "masking is one of the few interventions that still makes some sense".
"Each has unique personal issues."
It was up to them whether they shared their conditions.
Chhour, who is an asthmatic, said she struggled with wearing a mask because of her medical issues but persisted because she wanted to set an example and protect others.
But she had had surgery on her nasal passages last year and breathing through her nose was very difficult.
She applied for an exemption under the Covid orange traffic light setting.
"But I also think the Government made it way too easy to get these exemptions so people who have true exemptions are looked on as faking it."
She said she sometimes gets hassled on planes from other passengers despite wearing an exemption badge.
"When I say 'look I have an exemption' they roll their eyes and go 'yeah right'."
Chhour, however, says feels the responsibility of having a mask exemption and tests for Covid before every flight she takes to ensure she is negative.
"That's how I found out I had Covid this week, before a flight and it came up positive.
That just shows that being vigilant and doing what I'm supposed to do did protect people, because that was my responsibility."
Simon Court said that a few months ago, he started feeling unwell wearing a mask, particularly for a long period of time.
"Over the years I've had to work pretty hard with my fitness because when I was in my 20s, I contracted meningitis and it devastated my health. I spent three weeks in a coma and I've got permanent heart and lung damage as a result.
"While I do work hard on my fitness, if I have to wear a mask for any length of time, I start to feel unwell so I got some advice that I could apply for an exemption so that's what I did."
James McDowall said he wore a mask more often than not.
"I sought a mask exemption to help at certain times of the day when my heart rate is soaring as a result of both a medical condition and the medication used to treat it.
"My high heart rate is further exacerbated by wearing a mask. In the past I've pushed through and kept it on, however the resulting headaches, breathing difficulties, and in some cases mild bouts of anxiety, were just getting too much."
He said he encouraged people to wear masks to help protect against Covid-19.
"And I should note that I do wear a mask more often than not – it really depends on my situation."
All three are first-term list MPs.