Homeowners have questioned the safety of a new range of green boilers that have been installed in Birmingham schools.
The worries are due to the soot and dust generated by the appliances, with resident Darren Plester telling the Birmingham Mail that the substances will adversely affect those with breathing difficulties.
His worries were addressed by the council, which advised that the equipment should be fitted with caution.
A council representative told the newspaper: "Should we identify issues through our monitoring, we would take action to ensure problems were averted and the health of the public was not compromised."
The biomass boilers are seen as being cheaper to run than other options and burn wood pellets, chips or logs to supply heat, while releasing a lower amount of carbon dioxide.
Efficient boiler use has been promoted in a study by the Carbon Trust, which found that UK organisations could save over £400 million yearly by taking simple measures to improve their use of the appliances.