Hastings Demolition, owned by Graeme Hall, was sentenced and fined $11,900 by Judge Melinda Dickey.
The charge carries a maximum fine of $600,000.
Hastings Demolition employed workers were at a Tawanui Developments-owned property in Tangoio, less than 1km from State Highway 2, when they lit the fire at 10am.
A call was made about the fire to a HBRC Environmental Officer at 12.50pm.
The company said the fire had been started by its onsite foreman, with the intention to burn native timber stripped during demolition.
The company claimed two casual employees loaded the fire with toxic material while the foreman, who left soon after, was attending a meeting at Napier Airport.
However, counsel noted the foreman who directed the fire be lit had returned from his meeting an hour before the regional council's enforcement officer, yet the fire was in full blaze.
The company admitted it was responsible for the acts of its employees, but submitted the incident occurred as a direct consequence of employees not following strict company policies and instructions given on the day of the incident.
The company believed that with clear instructions given to its employees, it could rely on them to follow those instructions.
HBRC principal scientist air Kathleen Kozyniak said the burning of the items is not only associated with nuisance dense smoke, but also emissions of hazardous air pollutants known to cause cancer or serious health effects.
The company had never been prosecuted prior to the incident but did receive a formal warning in 2018 for burning waste.
HBRC chairman Rex Graham said it was pleasing to see pollution being taken seriously.
"I hope this fine makes other people stop and think before they carry out any illegal burning," he said.
Earlier this year, another company was fined $12,555 for an illegal fire in Frimley, Hastings.
Pollution response and enforcement team leader Mike Alebardi said HBRC is committed to enforcing the rules that protect the health of the environment and community.
"This kind non-compliance is unacceptable, and we've shown the regional council will pursue these activities through the court if necessary," he said.
"It's one of the strongest signals we can send to discourage others not to burn prohibited items."
Anybody with information regarding unauthorised discharges to land, air or water is asked to contact HBRC's 24/7 Pollution Hotline.