Fertiliser company Ravensdown has been fined $1000 after an illegal discharge of sulphur dioxide earlier this year.
The penalty came with an infringement notice issued by the Hawke's Bay Regional Council after the discharge exceeded allowable limits in April.
A council spokesperson said the council operates an air quality monitor at Awatoto to measure concentrations of particles in ambient air in this industrial and coastal area.
The monitor could detect pollutant particles emitted from industry as well as windblown dust and sea salt.
In one hour-long period in April the sulphur dioxide averaged 620.5 micrograms, exceeding the National Environmental Standard by 50.6mcg.
It came from the cold-starting of Ravensdown's acid plant, in which sulphur dioxide release is normal but limited by the air quality standard and resource consent conditions.
The council had taken enforcement action, issued the notice, and had since received the fine.
Another "exceedance" was recorded on June 12, when pollutant particles were 57 micrograms per cubic metre of air, just over the limit of 50 micrograms per cubic metre.
But it was due to sea salt from a stormy sea and onshore wind, the statement said.
Ravensdown also operates an air quality monitor as part of its consent and provides data to the regional council.