St John crews in Auckland now have to wear full airborne personal protective gear to every callout.
This means gowns, eye protection such as face shields, gloves and N95 masks, all replaced after each patient.
As of yesterday, St John had 93 staff in self-isolation due to community contact with Covid-19.
The emergency service said most of these workers were temporarily stood down, pending negative tests, after patients gave inaccurate answers to Covid-19 screening questions.
Deputy chief executive Dan Ohs said staff were seeing about three to five people a day with Covid, including transfers to and from MIQ, but they were highly experienced with infection control in ambulances.
"We've got what would best describe as a bug bomb, we try to use that as much as we can. Any time we interact with a patient who we know to have Covid, we do our equivalent of a deep clean."
St John gets hundreds of calls a day and it takes staff, on average, an extra seven minutes to finish each callout in Auckland when completing Delta screening, cleaning and PPE use.
Ohs said ambulances would attend callouts, regardless of the Covid-19 status of patients, but they needed members of the public to be honest about their symptoms and Covid-19 exposure.
"We are really asking the public to be really open with us."
It is not mandatory for St John staff to be vaccinated but all have been offered injections, and management estimates more than 90 percent have taken them up so far.
St John is currently collecting the vaccination status of every staff member.
First Union ambulance co-ordinator and former St John staffer Faye McCann supported the ambulance service's decision to elevate PPE use in Auckland.
She said it had been a difficult time for staff who had needed to self-isolate after exposure.
"It's obviously very frustrating for them because this then goes on to their families, so their families also have had to self isolate. A lot of our members also live with other essential workers."
Wellington Free Ambulance medical director Andrew Swain said his colleagues were checking the latest WHO, Ministry of Health and CDC guidelines daily, and incorporating them.
He said crews adjusted their PPE depending on the callout, language barriers, a patient's consciousness and the treatment they required, rather than wearing the most extensive option every time.
"In a cardiac arrest, there are certain things that need to be done as immediately as possible. These include chest compressions and defibrillation and that can be done with a base level of PPE. Then the second crew will have the full PPE on and they will be able to deal with the patient's airways and breathing which of course is potentially more threatening."
Auckland emergency nurse and Auckland University lecturer Dr Natalie Anderson said people weren't normally thinking their best in health crises and Delta made it even harder to process patients at hospital.
"We're wearing masks which makes it very difficult for people who are used to partly reading lips and sometimes we would perhaps be more dependent on family members to help us translate some of those ideas. So just be patient with the process of screening. It is going to take an extra couple of minutes for us to just to be really sure that we are caring for people in the right places."
She said the health system was already stretched before Covid-19 so infection protocols were needed not only to protect patients but also first responders.
"People need to recognise that we are a precious commodity and we're a limited commodity, we are not drones that are just going to step up. There are no people to replace us if we get sick."