CHICAGO (CBS) — With COVID-19 cases surging, the Chicago Teachers Union is urging Chicago Public Schools to test school ventilation systems before students return to in person learning next month.

On Wednesday, an air safety expert working with the union expressed some of his concerns.

READ MORE: Supt. Brown On Making Improvements Within CPD: 'We Have To Gain The Community's Trust'

“There is no indoor air quality monitoring,” said Sterling Laylock, an environmental building consultant. “How will we know where we are, and how will we know what we are doing? And how will be we be able to make any corrective action?”

READ MORE: This Earth Day, Gov. Pritzker Signs Executive Orders To Keep People's Utilities From Being Cut Off, Move State Government Toward Using Low- Or Zero-Emission Vehicles

CBS 2 reached out to CPS for a response. A CPS spokesperson said that since the beginning of the pandemic, the district has followed the best available guidance from experts and scientists. And numerous studies showed classrooms can safely re-open with proper mitigation strategies.

MORE NEWS: Chicago Weather: Rain On The Way

Also From CBS Chicago: