Classrooms in England need air filters and monitoring devices fitted to protect children from Covid-19 and avoid further disruption to their learning, school unions have told the education secretary, Gavin Williamson.

The seven unions – representing teachers, school leaders, administrative and support staff – have written to Williamson asking for “urgent action” to improve ventilation when schools reopen for the autumn term without any requirement for children to wear masks or be grouped in “bubbles”.

The letter, backed by the Liberal Democrats, asks for air purification units to be installed to filter out the virus, as well as carbon dioxide monitors to measure airflow. It follows mounting evidence that coronavirus is transmitted primarily through airborne particles in enclosed spaces.

“There is a strong possibility of steeply increasing Covid cases in the autumn, with some children suffering from long Covid as a result. There are also concerns about a new wave of other respiratory diseases such as flu and RSV which are worse for children than Covid,” the letter warns.

“School staff, some of whom will not be double vaccinated, or are in a vulnerable group, are also in some cases still at risk of serious illness. Staff who are fully vaccinated are also still at risk of catching the virus and potentially developing long Covid, which is already afflicting tens of thousands of school staff.”

The group told Williamson it was “very concerned” that the Department for Education (DfE) had not provided any specific funding for schools to improve ventilation since January. The signatories include Unite, the National Association of Head Teachers, the Association of School and College Leaders, the NASUWT, the National Education Union, GMB and Unison

The DfE said: “We want to ensure schools are both safe and comfortable for students and staff – and good ventilation has consistently been part of government guidance. Areas where ventilation is poor should be proactively identified so that steps can be taken to improve fresh air flow if needed.”

The DfE and the Department for Health are running a GBP1.75m pilot scheme in Bradford to assess the most effective use of air purification technologies within schools.

Patrick Roach, the general secretary of the NASUWT teaching union, said a commitment by the government to fund improved ventilation would be “an extremely positive move. It would be reassuring to those working within our schools and be reassuring for many parents.”

Separately, a coalition of fire safety and education organisations have asked the government to mandate for sprinklers to be included in all new and refurbished school buildings in England.

The group, including the National Fire Chiefs Council and the Royal Institution of Chartered Surveyors, said the government’s latest plans would leave “the majority of schools exposed to fires”, with sprinklers only compulsory in boarding or special needs schools or in buildings over 11 metres in height.

The group said that in the five years to March 2020, firefighters attended fires at 1,467 primary schools and 834 secondary schools in England. Forty-seven primary and secondary school buildings were completely gutted and 230 others were seriously damaged.