Calls for updating laws on burning banned domestic fuel have been made after it emerged only one fine has been issued for the practice in 25 years.
People who live in Newport, Wrexham, Swansea and Flintshire, cannot burn some fuels like wood or coal – but only materials on an approved list.
The Clean Air Act was introduced by the Welsh Government to combat pollution.
Huw Morgan, of the Welsh Pollution Expert Panel, said officials should be allowed to go into people’s homes.
The only fine handed out was by Wrexham council, which issued a £2,500 penalty notice to a person who had been burning cables.
In smoke control areas (SCA) it is an offence to emit smoke from “a chimney of a building or a chimney serving a furnace of a fixed boiler or an industrial plant”.
Flintshire council handed out 39 warnings while Newport council has taken no action.
Mr Morgan said that he “was not surprised at all” that such little action had been taken as the smoke controls “do not make it easy to enforce anything”.
“They would have to really modernise the powers so we could go into homes and check what fuel people are burning,” he said.
“People are ignorant of how to burn wood correctly. The big problem is that people are burning wet, or unseasoned wood logs which gives off light coloured smoke which is worse for the environment.”
The 1993 Act, which does not cover the capital city Cardiff, “needs updating and should apply to all areas”, according to Mr Morgan.
But he said that the main issue for air pollution is road vehicles.
Cardiff Council acknowledged the difficulty in enforcing SCAs and said it would wait for a new act before deciding whether to implement one.
The Welsh Government is working with key stakeholders in the industry to develop a “comprehensive package of interventions” to domestic fuel burning, while saying it was “acutely aware” of the act’s limitations.