Two people have been treated at hospital after inhaling smoke from the Christchurch Port Hills fire and a third after injuring his ankle.

"[We've had] one male - a walk-in presentation - who rolled their ankle while evacuating. They're okay," said a spokeswoman for Christchurch Hospital.

"We had a firefighter present for smoke inhalation - they're also okay now. And we've had one male child - 9 years - present for asthma being exacerbated by smoke."

The Canterbury District Health Board and the Asthma & Respiratory Foundation have issued warnings about smoke inhalation.

Even those who are some distance from the fire may be at risk - from wind-borne ash particles and smoke.

Those at greatest risk from inhaling the fire's smoke are cigarette smokers, the elderly, children and those with heart disease, asthma or other lung disease. People should seek medical help if their symptoms get worse, especially if they have asthma, lung or heart disease, or if they experience breathlessness or chest pain.

"People are advised to minimise their exposure to smoke and time spent outdoors," the foundation says. "Windows and doors need to be kept closed, air vents blocked, and air-conditioning set to a recycle setting."

It added "those with asthma and respiratory conditions in the Christchurch area [need] to be prepared, as bush-fire smoke can trigger asthma attacks, allergies and shortness of breath.

"The smoke from bush fires contains small particles that can cause irritation to the lungs, eyes, nose and throat."

The DHB wants people to phone their GP first if the smoke is causing breathing problems, unless it is an emergency, in which case they should immediately call 111.

A medical officer of health, Dr Alistair Humphrey, said that for most people, the smoke, while unpleasant, would pose no risk to their health.

"Smoke may irritate the eyes, nose, throat and airways. More serious symptoms include runny or sore eyes, dry or sore throat, sore nose, cough, tightness of the chest or difficulty breathing.

"In healthy people, most symptoms disappear soon after exposure to smoke ends and do not cause long-term health problems."

Dr Humphrey also encouraged people to look out for their neighbours, especially the elderly and those with disabilities.

""We all need to remember to look out for one another and take care of each other."

Advice for asthmatics:

• Keep taking prevention medication as prescribed
• Carry a reliever inhaler
• Use the reliever as soon as symptoms appear, preferably with a spacer
• Call 111 if the reliever doesn't help, or is needed more than every 2-3 hours

- NZ Herald