What's In Your Air?

Clean indoor air is an essential part of building sustainability as well as occupant health and productivity. Ventilation systems monitor and regulate the airflow, and New York’s energy code has extensive rules on ventilation efficiency. However, most buildings are only designed to minimize adverse health effects such as shortness of breath or sick building syndrome, and little is known about the air quality inside buildings once people move in.

Since we spend most of our time indoors, we decided to take a closer look at what we’re actually breathing here at our own office at 55 Broad Street in Manhattan’s Financial District.[1] We breathed a sigh of relief at the results: very low levels of pollutants linked to long-term health problems. But the carbon dioxide (CO2) levels, which can affect cognitive abilities in the short term, varied widely throughout the workday. In response, we learned how to better manage and lower indoor CO2.


The healthy renovation choices Urban Green made in 2016 and Rudin Management’s attentive operations and maintenance has led to excellent overall air quality. We used  Airthinx monitors to track two types of harmful pollutants—volatile organic compounds (VOCs) and particulate matter (PM).

VOCs include a wide range of airborne substances, including formaldehyde, benzene and toluene. Formaldehyde is highly toxic and used to make glues and plywood - key components of most flooring and furniture. It has a strong smell and can irritate skin and eyes.[2] During our renovation, we chose no or low-VOC paint, Cradle to Cradle Certified and low-VOC carpet tiles from Shaw, and gently-used furniture donated by Google and Kimble. These choices meant that we wouldn’t need to worry about harmful chemicals off-gassing, and as expected, every room in our office had very low or undetectable levels of VOCs.

The level of particulate matter (PM) is also very low in our office, always remaining below the National Ambient Air Quality Standard during work hours.[3] However, a curious pattern developed on many evenings after staff had left. Levels of PM often rose after dark and peaked sometime between 9 p.m. and midnight at levels as high as 45 µ/m3.

A New York State DEP outdoor air quality monitor at Division Street, near the Manhattan Bridge entrance, also reported increased levels of PM at these times. It’s likely that these particles entered the building from outdoors, but their origin is unknown. Diesel-powered garbage trucks are one possible explanation. These trucks collect trash from commercial buildings each evening, then idle while the garbage is compacted. The emissions from the diesel engines--a dozen or more that cram into the narrow streets of Fidi—contain fine particulates that seep in through the building’s single-pane windows that are over 50 years old.



Humans contribute to indoor CO2 levels with each exhale. Historically, we thought high levels of CO2 in a space simply meant that the air was ‘stale’ but not harmful. But recent research by Harvard University now establishes a link between elevated CO2 and diminished cognitive abilities.[4]

For reference, Earth’s atmosphere has a CO2 concentration that currently hovers above 400 parts per million (ppm), and hit 415 ppm this year for the first time in human history.[5] In our open office space we have  up to 20 people that type, talk and pace throughout the day. A consistent daily cycle emerged: CO2 levels fell to 405 ppm at night, peaked around 750 ppm at 2 p.m. and then slowly tapered off as people left the building.

There were a few events that caused CO2 levels to rise above 800 ppm, which is still below levels expected at the ventilation rates recommended by ASHRAE. Though rare, these problems usually occurred when the occupant density rose above one person for every 50 square feet. The highest CO2 levels were recorded if meetings ran past the evening shutdown time for the ventilation system.



With indoor air quality playing an important role in short-term cognition and long-term health, understanding our office air quality is incredibly valuable. Our carpet, paint and furniture renovation decisions were validated by the lack of VOCs. The particulate levels in our space appear to be driven by poor outdoor air quality rather than internal factors. Finally, the levels of CO2 in some of our meetings have led to us to make changes. We consider headcount and room size when scheduling meetings, we leave doors open whenever possible, and we upgraded the air supply to our largest conference room.


In the future, we would like to conduct controlled experiments to see the impact of increased ventilation on occupant density. Then we can compare our office space to the current ventilation design standards and see if updates are needed for better air quality. We’d also be interested in exploring the potential of plants and plant walls to remove VOCs in offices.

[1] Thank you to Airthinx for allowing us to use their air quality monitoring devices and helping us interpret the data. For over six months, three Airthinx monitors were used to track levels of formaldehyde (and other VOCs), CO2, particulate matter, temperature, pressure and humidity at one-minute intervals in air we breathe at work.

[2] Long-term repeated exposure to formaldehyde can lead to respiratory problems and potentially cancer. https://www.atsdr.cdc.gov/PHS/PHS.asp?id=218&tid=39

[3] NAAQS is the EPA’s standard for outdoor air quality - it limits PM by micrograms per cubic meter of air (µ/m3). Fine particulates (PM2.5, particles with a diameter less than 2.5 microns) are the most harmful and their levels may not exceed 12 µ/m3 on average over a year or 35 µ/m3 in any 24-hour period.

[4] The COGFx study observed the cognitive abilities of 24 test subjects over six days in a controlled laboratory environment with varied levels of carbon dioxide, VOCs and overall ventilation. Occupants that breathe air with increased CO2 levels (400 parts per million, or ppm, or higher than normal) tend to be less alert and scored lower on cognitive tests. https://ehp.niehs.nih.gov/doi/10.1289/ehp.1510037

[5] The NOAA observatory at Mauna Loa recorded the atmospheric concentration of carbon dioxide at 415.26 ppm on May 11, 2019, and it also recorded the first time the concentration averaged 411 ppm over a month. https://scripps.ucsd.edu/programs/keelingcurve/2018/06/07/another-climate-milestone-falls-at-mauna-loa-observatory/


About the author

Sean Brennan
Sean leads Urban Green’s Research team. He is responsible for identifying and executing studies that reveal industry trends and influence building design. He has worked in the energy and utility space for over 10 years and has specialized in building science and analysis. Sean has improved energy efficiency and asset maintenance programs at Pacific Gas & Electric and Sempra utilities in California.