A person who collapsed in a critical condition after being “overcome” by chemical fumes at a Christchurch workplace “is now stable in hospital”, police say.

Firefighters rescued three people who were affected by the chemical spill at the Sydenham workplace on Thursday.

Emergency services were called to the incident at Solvent Rescue on Coleridge St about 3.22pm.

Fire and Emergency NZ assistant district commander Michael Balmer said crews found one person unconscious at the scene.

"On arrival they discovered there were chemicals involved; they made a very snap rescue.

"The crews did a great job in getting the patient out of the danger area and into fresh air.

"It was a liquid product but it gave off vapours, I believe, that affected the individual and they collapsed inside the building."

Solvent Rescue recycles paints, cleaning and waste products, and other solvents.

"We were able to isolate the systems involved so that it wouldn't escalate any further, once the chemicals were isolated power was isolated to that section of the factory," Balmer said.

"We were able to determine that the product wasn't a huge amount but it was safe enough to then hand back to the property representative."

Balmer said the firefighters responded to a difficult situation well.

"You turn up to incidents like that, chemical incidents, and you're going into the unknown really so it's quite a high risk environment. I was very proud of the way the crews responded to that."

A police spokesperson said on Friday morning the patient who was in a critical condition after the incident was “now stable in hospital”.

Hato Hone St John said ambulance staff treated three people and took them to Christchurch Hospital.

“Two patients were in moderate condition.”

Police managed traffic at the scene. Nearby businesses were told to shut their doors and windows and stay inside during the incident.

On Friday, Fire and Emergency NZ said the scene was handed back to the business at about 7pm.

A Fenz spokesperson said eight fire engines were sent to the “hazardous substance” incident.

Five crews from the Christchurch City, Spreydon, Woolston, Wigram, and Ilam stations responded, along with command and hazardous materials units.

The spokesperson said firefighters had to force their way into the commercial property to rescue two people affected by the chemicals. Several others were evacuated from the building.

Solvent Rescue’s website says it is an “independently owned and operated specialist solvent recycling and liquid purifying plant”.

"Currently our specialities lie in recycling all Printing & Paint solvents, Drycleaning waste, Special Cleaning Solvents and Liquid Purification. However, our technology is constantly evolving and we are always interested to test any other solvents, to see if they are suitable for recycling,” the website said.

“We are an environmentally friendly company and delight in doing our bit to reverse climate change. Turning your waste into environmentally acceptable material would be our pleasure.”

-Allied Media and RNZ