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  • Writer's pictureNikki James Zellner

Indoor Air Quality monitoring for carbon monoxide in schools

Screenshot of indoor air quality monitoring sensor data showing active sensors in Boston Public Schools
A screenshot of the Boston Public Schools Indoor Air Quality Dashboard on the morning of Sunday, August 27, 2023

CO2 Monitoring became all the rage with the initial onset of COVID-19 and the return to school efforts – but the real winners? Those school systems or buildings whose IAQ sensors include data for carbon monoxide, not just CO2, humidity, and temperature.

In 2022, Boston Public Schools made a splash with their state-of-the-art IAQ dashboard. In partnership with Ecomesure and SGS, the BPS school system gave the public what they didn't know they needed, but was trendily demanding: real-time transparency on indoor air quality in schools.


Indoor Air Quality sensors were installed in all BPS classrooms, Nurse’s Offices, and Main Offices, with a roof-top unit installed in every school building to measure outdoor air as a baseline per location.

The sensors report information in real-time on key measures of air quality. The data collected from these sensors helps BPS identify, review, and respond to indoor air quality and temperature issues, and advocate for HVAC and other building investments to improve indoor environment quality.

Each sensor records the following IAQ measurements:

  1. Carbon Dioxide (CO2)

  2. Carbon Monoxide (CO)

  3. Airborne particulates - Total (PM10)

  4. Airborne Particulates - Respirable (PM2.5)

  5. Temperature (T)

  6. Relative Humidity (RH%)

BPS adopted IAQ standards following federal, state (MA), and local (Boston) recommendations on indoor air quality and ventilation in schools.

As it relates to Carbon Monoxide monitoring specifically, here is their approach, pulled from their Response Action Plan:

Carbon Monoxide (CO): Carbon monoxide is a colorless, odorless gas. It results from incomplete decay of carbon in combustion processes. Common sources of CO in schools are improperly vented furnaces, malfunctioning gas ranges, canned heat (e.g. a Sterno), or exhaust fumes that have been drawn back into the building. Worn or poorly adjusted and maintained combustion devices (e.g., boilers, furnaces), or a flue that is improperly sized, blocked, disconnected, or leaking, can be significant sources. Auto, truck, or bus exhaust from attached garages, nearby roads, or idling vehicles in parking areas can also be sources.
Carbon monoxide at higher levels is considered to be a serious health hazard. The carbon monoxide standards for indoor air quality are the U.S. Environmental Protection Agency (US EPA) National Ambient Air Quality Standard (NAAQS) of 9 ppm CO on a 8-hour time-weighted average (TWA), and the World Health Organization Guidelines for Indoor Air Quality – Selected Pollutants of 6 ppm. However, BPS Facilities will be notified and take action at an instantaneous measurement of 4 ppm as a more conservative and precautionary approach to this health-based standard.
● Typical: 0-4 ppm
● Moderate: 4-9 ppm
● High: > 9 ppm
Response Action to Exceedance:
A notification email will be sent to the school’s Principal/Head of School and the school email account. All notifications will contain the list of affected rooms with the elevated CO level(s). In the event of an emergency, a notification phone call to the school and the school’s designated Operational Leader will be made with immediate response action instructions.
Because the CO standard is health-based, the notification process and action(s) will be based on the first exceedance of an instantaneous 4 ppm measurement. Response action(s) shall include, but not be limited to, an investigation by the BPS Environmental and HVAC Divisions to identify and control the source of CO. The investigation may include monitoring real-time instantaneous CO results, monitoring trending 8-hour time-weighted average CO results, investigating HVAC equipment (e.g. boiler, radiators, etc.), and making recommendations to achieve optimal ventilation, as described above in Section II. Manual CO measurements may also be required to ensure the IAQ sensor(s) is within calibration. If the IAQ sensor(s) is found to be outside calibration (+/- 20%), the sensor(s) shall be recalibrated by SGS Galson and CO measurements re-verified.
In the event of an emergency, the response action shall require immediate action by the school, including, but not limited to, relocation of staff and students, possible evacuation of the classroom or school, notification to the Boston Fire Department (BFD), and any action(s) required by BFD.

What I love to see?

How low those ranges are and what qualifies as exceedence. Here's why: Most personal CO alarms are not required to alert until 72 ppm has been reached over a cumulative amount of time – relying on life-threatening, acute exposure to prompt concern alert and concern.

But these lower ranges are in-line with most carbon monoxide safety advocates' requests for alarm standards, require a lower-set point to alert occupants that they are being exposed to a toxic gas earlier, and to make any necessary updates to equipment failures or deterioration before it becomes a long-term chronic or life-threatening acute exposure issue.

Where I think this plan misses the mark...

Schools would be responsible for taking action to notify the Boston Fire Department. How can you notify emergency services if your students and faculty are impaired? Too big of a risk. If you're trying to set a "best practice model" it would be that anything over a certain ppm immediately auto-notifies emergency response teams and school-wide immediate evacuation become mandatory.

In addition, based on where these sensors were placed (classrooms, nurse's office, administrative offices) – gymnasiums and cafeterias – two of the biggest locations that show up when it comes to our database of school carbon monoxide incidents, are not included in sensor representation from what I can tell. This means the most used gathering spaces (for school-use and community-based events) are left in the dark when it comes to real time data.

A graphic showing how schools report sensor data to primary dashboard, community, and partners for data analysis
An overview of how IAQ monitoring works in BPS schools


Once you click on a school inside the IAQ dashboard, you can see the overview, latest sensor results, and a 30-day report for air quality – not only in the school, but down to the classroom level.

A chart showing moderate alert level of CO in McKay K-8 school
Real-time data from McKay K-8 school shows carbon monoxide levels have risen to "moderate level of accumulation" at 5.4 ppm in Classroom 13 at 9:37 a.m. on Sunday, August 27

A chart showing indoor air quality measurements at Kennedy Academy for Health careers; carbon monoxide is showing a moderate range of 7.5 PPM (increased CO) in classroom 109 at 9:30 Sunday morning
Real-time data from Kennedy Academy for Health Careers (Grades 9-10) shows carbon monoxide levels have risen to a "moderate level of accumulation" of 7.547 ppm at 9:38 a.m. on Sunday, August 27

Chart showing classroom air quality at Murphy K-8 school, indicating carbon monoxide has increased in classroom 108
Real time sensor data at Murphy K-8 pulled on Sunday, August 27 at 11:58 am, showing Carbon Monoxide accumulation of >19ppm

I include these three screenshots for a reason.

First, What was happening at 9:37 a.m. on Sunday, August 27, inside these two classrooms (at two separate schools) that caused their carbon monoxide levels to increase by 5-7 ppm.

And what exactly happened to increase Murphy K-8's CO level by 19?

For every classroom, you're looking for CO level to be in "typical range" i.e. under <4 ppm, but on average it shouldn't go above 1-2ppm.

But looking the latest sensor reporting for all schools on the Live dashboard, two schools had Yellow (Moderate) alerts – McKay K-8 and Kennedy Academy for Health Careers (Grades 9-10 only) within 5 minutes of a previously normal reading, and one school had Orange (High) alerts – Murphy K-8.

For McKay, the CO level in Room 13 jumps from .5 ppm to 5.418 ppm.

For Kennedy Academy, the CO level in Room 109 jumps from .5 ppm to 7.5 ppm.

For Murphy, the CO Level in Room 108 jumped from .1 ppm to 19.7 ppm (well into the high-range, and anyone in that room would be experiencing mild symptoms of CO exposure)

If I were maintenance or school officials, I'd be looking at:

- What was running at the time (HVAC)?

- Were any appliances in use (in this or other classrooms nearby, in cafeteria, in laundry)?

- Were any portable gas-powered devices in use (for construction, landscaping, cleaning)?

- Were any vehicles (bus, delivery, personal) idling in close proximity to this room?

It's these little glimpses of real-time information that can help you narrow down the real sources and spreaders of Carbon Monoxide in your buildings and campuses – if only you're doing more than looking at data, but actively tying it to what's going on in and around the property.


The reality of having a state of the art IAQ sensor system is – not every school system has the funds to put it into play.

It certainly wasn't an inexpensive undertaking for Boston Public Schools, their funding and grants included:

  • Winning a $15.4M IVAQ grant from DESE to design and install new mechanical ventilation systems in 5 non-mechanically ventilated elementary schools

  • Securing ESSER funding to connect the IAQ sensors to the Building Management System

  • Applying for the U.S. Department of Energy’s Renew America’s Schools grant

But the installation paid off. Boston Public Schools has now set the example for how schools can not only create safer spaces, but create change in the conversation and outcomes, not only in the U.S. but the world:

  • Been awarded Best in Class - Energy Efficiency Plus Health from the 2023 U.S. Department of Energy’s Efficient and Healthy Schools Campaign

  • Influenced technical assistance for K-12 schools - White House COVID-19 Taskforce and Office of Science and Technology Policy (Clean Air in Buildings Challenge), U.S. EPA, National Caucus of Environmental Legislators, Environmental Law Institute, U.S. Green Building Council, Center for Green Schools, MA DESE IVAQ Grant

  • Joined the White House Clean Air in Buildings Challenge and signed the Pledge

  • Participated in U.S. Department of Energy (DOE) Schools Focus Group and joined the DOE’s Efficient and Healthy Schools Campaign

But the real reason this is a win?

– Its students are safer

– Its faculty and staff are safer

– Its community is safer

This is a huge step in the right direction, and that's what matters most.

* * * *

Nikki James Zellner is founder of CO Safe Schools, a mom of two CO-poisoning survivors, and advocate for safer schools.

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