A major six-month project to test the air quality on one of Powys' busiest roads is about to begin.
There are calls for a bypass in Newtown
Sensors will be used to measure pollution in New Road, Newtown, in the first scheme of its type in the county.
Powys Council said there were concerns about levels of nitrogen dioxide, a pollutant linked with exhaust fumes.
Some of the devices will be placed in residents' gardens along part of the A483 through the town.
Routine samples taken by environmental health officers had led to concerns in New Road.
The council said it would have to decide how to control emissions if air quality was discovered to be below national standards.
A spokesman said: "The air in New Road is being monitored closely to allow comparisons to be made with national objectives."
Traffic levels in Newtown have been a controversial issue for many years.
County councillor Richard Noyce, who is calling for a town bypass, said in January that Newtown was in danger of being "choked by traffic".
He said the council's air quality tests could reinforce calls for a new road.
"If pollution is consistently high then that does strengthen the call for an alternative road system for Newtown," he said.
The assembly government said earlier this year that a transport appraisal had been carried out, and a scheme to improve the town's traffic flow was part of its programme to upgrade trunk roads.