CHICAGO (CBS) — Chicago Public Schools officials on Wednesday announced that a recent evaluation of every school campus has determined the vast majority of classrooms are “prepared for safe occupancy” as the district plans to have some students return to in-person learning during the second quarter.

CPS also announced it will spend $8.5 million to provide more than 20,000 HEPA air purifiers for every classroom.

“Nothing is more important than creating the safest possible in-person learning environments for our students and dedicated staff, which is why we are going beyond public health recommendations to place HEPA air purifiers in every classroom,” CPS Chief Executive Officer Janice Jackson said in a statement. “Combined with critical mitigation efforts, such as mask-wearing, readily available hand sanitizer, signage and social distancing, the district’s plan supports a safe return to school.”

CPS students have been learning entirely remotely since April due to the pandemic, and the district said it has since hired an independent state-certified environmental hygienist to conduct an air quality assessment of all 513 district-run schools in order to ensure they’re safe before bringing any students back to classrooms.

According to CPS, that assessment determined 94% of the 36,000 spaces assessed in its building were cleared as safe, including 99% of the nearly 20,000 classrooms checked.

“To meet ventilation requirements, a space must have functioning mechanical ventilation, which is defined as the ability to both move air in and out of the room, or have a functioning window with one or more supplemental air purifiers, depending on the size of the room,” the district said in a news release.

CPS said 91% of all classrooms have functioning mechanical ventilation. The rest have working windows and air purifiers. No students will be placed in classrooms that have not been cleared.

“CPS is taking the necessary steps to create the safest possible environment for in-person learning, which is essential to the healthy development of young people in our city,” Chicago Department of Public Health Commissioner Dr. Allison Arwady said in a statement. “In private and parochial schools that are in session, as well as other states where in-person learning is occurring, we have seen very little transmission of COVID-19 in those settings.”

The results for each individual school have been posted on the district’s website, at cps.edu/airquality.

Officials said six CPS schools recently were under active construction, and their assessments will be completed soon and posted on the website.

The district has announced plans to bring back students in pre-k and some special education cluster programs for in-person learning during the second quarter, which begins Nov. 9, although officials have yet to announce a start date for their limited in-person classes.

CPS said their phased reopening plan will bring back preschool and most special education students for five days a week of in-person learning, while all other students will continue remote learning for the second quarter. CPS said some of its specialty schools may follow a hybrid model.

Parents who are not ready to send preschool or special education students back to in-person learning were allowed to opt out by Oct 28, and continue remote learning during the second quarter.

The Chicago Teachers Union has pushed back on plans to bring any students back to classrooms in the second quarter, noting COVID-19 cases have been surging in Chicago in recent weeks.

CTU has accused CPS of illegally refusing to bargain over plans for how and when to safely reopen schools, and the union is seeking an injunction to block CPS from moving forward with any reopening efforts.

The union has filed an unfair labor practice complaint against CPS with the Illinois Educational Labor Relations Board (IELRB), accusing the district of violating their collective bargaining agreement with CTU by failing to negotiate the terms of reopening plans.

Last month, an independent arbitrator ruled that CPS can’t require clerks and other school employees to report to school buildings if it’s feasible to work remotely. In its complaint with the IELRB, the union said documents subpoenaed from CPS during that arbitration process revealed “hundreds of schools had serious maintenance problems in their ventilation systems.”

The union said CPS records show 60% of the district’s school buildings have no central HVAC system, 50% have non-functional critical components of their ventilation systems, and only 9% have air filtration systems that meet public health recommendations for COVID-19 safety.

CTU said it sought permission to inspect 13 schools with serious maintenance issues in their ventilation systems, but CPS denied their request. The district, however, has said the union has no legal or contractual right to conduct its own inspection of schools.

CPS spokeswoman Emily Bolton last month accused CTU of trying to “obstruct and mislead the public about the necessary planning measures needed to prepare for a potential return to safe in-person learning.”