Radon levels reduced at Highland Council schools
Tests on four council buildings previously found to have unacceptable levels of radon have shown a significant drop in the gas.
Contractors carried out work to reduce levels at Helmsdale's library and primary school, Halkirk Primary and Glen Urquhart High School.
Highland Council has sought further advice on controlling radon at the high school in Drumnadrochit.
Radon is a naturally occurring radioactive gas.
Exposure to high levels can pose health risks. Highland Council and NHS Highland have previously said the risks at the sites tested were "very low".
Last month, the local authority said checks would be made at 34 of its other schools and in August it announced tests would be done at 1,150 council houses.