Carbon Dioxide: The Invisible Indoor Air Pollutant in California's Classrooms



By Jessica Aguirre, Josh Slowiczek, Mark Villarreal and Michael Horn

Poor ventilation and air quality in California's schools could be impacting students' health and academic performance. Jessica Aguirre reports.

researchers from the Lawrence Berkeley National Lab and UC Davis recently released a study looking at ventilation in California schools – several right here in the Bay Area. Their findings: 85 percent of classrooms had levels of carbon dioxide, or CO2, above acceptable levels of 1,000 parts per million, having the potential to impact students’ health and academic performance.

“We were shocked,” said Wanyu Rengie Chan, one of the lead researchers of the study, “We were not expecting it.”

They were not shocked because of the issue itself, which has been studied for over a decade now, but shocked because the classrooms they monitored newly-installed Heating, Ventilation and Air Conditioning units, or H-VACs. Chan says they believe the issue is largely due to improper installations, programming and maintenance, which she believes is largely due to a lack of awareness on the part of the schools and their districts.

HVAC Issues Resulting in High CO2 Levels

  • Problems with installation of HVAC Systems
  • Incorrect HVAC Systems purchased
  • Improper controls and thermostats
  • No follow-up testing after installation
  • Poorly-maintained filters

Source: Ventilation Rates in California Classrooms study

But NBC Bay Area’s Investigative Unit was able to track down one school district in Santa Clara County where students and staff have been taking notice, and steps to address it.

“I noticed that when the teacher closes the door, first it gets stuffy in the room. It gets hot and stuffy. And students tend to want to sleep a little bit more,” said Emily Chien, a senior at Piedmont Hills High School in San Jose. “They put their heads down. They close their eyes. And they’re in general not as attentive in that classroom.”


Sometimes when it gets stuffy in classrooms, it feels like it takes more energy to pay attention. And even when I try to, it just feels like the room is sapping this energy from me.

Chien and her classmates are currently working with Stanford’s Virtual Design Construction Program to research and understand the impacts of CO2 on students across the Bay Area. Part of that project includes looking at data the district is already collecting.

“As East Side updates its current controls that are outdated, we want to provide a healthier environment for students to help improve their achievement, and to provide a healthier environment to thrive in,” said Roger Silveira, the Director of Facilities Maintenance and Operations for East Side Union High School District, the largest of its kind in Northern California.

Silveira says he began being concerned about the issue of CO2 levels in classrooms roughly 2 years ago when he stumbled across a research paper from the University of California, Berkeley. Since then, he has been actively working to address it – describing it as his obsession.

About a year ago, that obsession manifested itself in programmable thermostats that also monitor C02 in classrooms. As of now, he says they are roughly 90 days away from monitoring every classroom across the district, which is home to 22,000 students.

Silveira says the initial monitoring showed that some classrooms were in the acceptable range, many were in the 1200 to 1300 range, and a few rare cases maxed out the monitors at 2000. But the new technology has allowed them to address the issue on a case by case basis, ensuring that students are getting plenty of fresh air.

It’s almost like, in a way, if you get enough CO2 in the room, that you’re almost intoxicated in a certain way. You can’t think as clearly. You can’t think logically. You can’t control your temper and your frustrations as much as you normally would be able to.

Silveira believes there should be both state and federal laws regulating CO2 levels in classrooms. Currently, the closest requirements are found in Title 24 of California’s building code – which advise indoor levels of CO2 should not exceed more than 600 to 700 PPM from outside, roughly 400 PPM. There is also a recent program from the California Energy Commission requiring that all newly-installed HVACs be tested by a certified technician, but that won’t be enforceable until there are enough people to manage the workload, which there aren’t.

Ryan Lundell, who has been at East Side Union High School District for the last eight years, thinks the issue of CO2 levels and air quality in classrooms needs to be a priority for schools around California

“I don’t care how great the teacher is or how excited the student is,” he said. “If that facility and that air quality is not where it should be, the learning isn’t going to happen.”