Formaldehyde in Focus: How New EPA Findings & ASHRAE’s Position Document on Indoor CO₂ Reshape IAQ Priorities

Discussions about indoor air quality (IAQ) usually focus on particulate matter and carbon dioxide (CO₂) with gases like formaldehyde and ozone treated as secondary contaminants. According to ASHRAE, the focus on CO₂ is misguided. Based on a December 2024 final risk evaluation from the U.S. Environmental Protection Agency (EPA), there should be more focus on formaldehyde and the significant health risks associated with this pervasive contaminant. Using air cleaning technologies like Sorbent Ventilation Technology^® with ASHRAE’s IAQ Procedure, you can proactively control formaldehyde and other harmful gases, as well as CO₂ if desired, while reducing HVAC energy use and cost.

Confusion About Indoor Carbon Dioxide

According to ASHRAE’s Position Document on Indoor Carbon Dioxide, “…the meaning of indoor CO₂ as an indicator of IAQ and ventilation is commonly misinterpreted within the HVAC industry….” The Position Document further states that, “ASHRAE Standard 62.1 has not contained a limit value for indoor CO₂ since the 1989 edition of the standard. Misunderstanding of previous editions of the standard continue to lead many to incorrectly attribute a 1000 ppm limit to ASHRAE.”

The latest version of Standard 62.1 (see Addendum ab to 62.1-2022) provides further clarification with the following informative note: “The CO₂ values in Table 6-1 [Minimum Ventilation Rates in Breathing Zone] are only for the purposes of implementing CO₂ DCV. They are not intended to be and should not be used as indicators of IAQ.” In other words, CO₂ may be used as a proxy measure for occupancy when “dilution ventilation” is the only means to maintain IAQ, but CO₂ alone is not a good IAQ indicator.¹

While acknowledging that indoor concentrations of CO₂ greater than 1,000 ppm have been associated with self-reported cases of sick building syndrome, the Position Document says that “these observations were not controlled for other contaminants or environmental parameters; therefore, elevated CO₂ concentrations likely served as indicators of inadequate ventilation that increased the concentrations of all contaminants with indoor sources.” The Position Document also points out that contaminants like formaldehyde that are emitted by building materials and enter from outdoors “do not depend on the number of occupants in a space” and therefore “are not correlated with CO₂ concentrations.”

After reviewing studies that investigated the cognitive effects of exposure to CO₂, ASHRAE found that “existing evidence for direct impacts of CO₂ on health, well-being, learning outcomes, and work performance at commonly observed indoor concentrations is inconsistent…” and requires further investigation. Currently, the only definitive limit on CO₂ comes from the U.S. Occupational Safety and Health Administration, which states that CO₂ is considered nontoxic at concentrations up to 5,000 ppm.

How ASHRAE Defines Acceptable Indoor Air Quality

Since the 2019 edition of Standard 62.1, IAQ has been defined by a list of “design compounds” and “design limits” prescribed in Table 6-5 (see below). This list was determined by the Standard 62.1 Research & Education Subcommittee based on a thorough literature review. If published data were sufficient to indicate a compound was likely to be found in any building type covered by the standard at potential harmful levels, then the contaminant was added to the list. ASHRAE’s goal was not to include every compound that may appear in indoor air, but rather to include a sufficient number and diversity of compounds such that the control of the compounds would result acceptable IAQ as per Standard 62.1.

In addition to Table 6-5, ASHRAE has published a spreadsheet to calculate ventilation rates according to the IAQ Procedure of Standard 62.1 that includes emission rates for all the compounds in Table 6-5 for various space types. This spreadsheet makes it easy to ensure design limits are maintained through a combination of outside air ventilation and air cleaning using technologies like Sorbent Ventilation Technology that are effective at removing all the Table 6-5 gases. When required, Sorbent Ventilation Technology can also be used to remove indoor CO₂.

In enVerid’s 10-plus years calculating the volume of outside air and air cleaning required to maintain the design limits in Table 6-5 for a wide range of space types, one compound has proven to be the most challenging to control and therefore the most important: formaldehyde. The new formaldehyde final risk evaluation from the EPA underscores the importance of controlling formaldehyde to maintain IAQ.

Formaldehyde: The Critical Contaminant

The EPA’s final risk evaluation determined that “formaldehyde presents an unreasonable risk of injury to human health under its conditions of use….” According to the EPA, “exposure to formaldehyde for a short period of time, such as for 15 minutes (called an acute exposure) cause sensory irritation such as eye and respiratory inflammation” and “Inhaling formaldehyde for longer ‘chronic’ periods of time can reduce lung function and increase asthma and allergy-related conditions, and cancer.”

A ProPublica investigation also published in December 2024 went further stating that “Formaldehyde is all around us and causes more cancer than any other chemical in the air. It can also trigger asthma, miscarriages and fertility problems.” Indeed, a key challenge with formaldehyde is that it is found nearly everywhere, and people are routinely exposed to formaldehyde in indoor and outdoor environments, often from multiple sources at a time. Formaldehyde is used to make many products found in daycare centers, schools, offices, warehouses, and most other indoor spaces. These products include composite wood products and other building materials, furniture, adhesives, paints, printer ink, plastics, textiles, toys, semiconductors, and personal care products. Formaldehyde is also generated when things burn, like when cars emit exhaust and through forest fires. Wildland-urban interface wildfires, likes those in Los Angeles in Janaury 2025, are particularly hazardous due to the burning of structures and vehicles.

The challenge with formaldehyde, in addition to its ubiquitousness, is that it is colorless and, so far, impossible to measure using standard IAQ sensors. According to Standard 62.1, Table 7-2 (see Addendum i to 62.1-2022), the accuracy of a “direct reading instrument” for formaldehyde (i.e., a sensor) must be +/- 0.1 ppb with a resolution of +/- 2%. enVerid has done extensive market research for a sensor that meets this requirement and has been unable to identify one. The only reliable way to measure formaldehyde is with air sampling using test methods defined in Table 7-1 of the standard.

In light of the EPA’s final risk evaluation for formaldehyde, IAQ discussions must expand beyond CO₂ to address compounds like formaldehyde, which pose undeniable health risks even at low concentrations. By leveraging advanced air cleaning technologies like Sorbent Ventilation Technology and using ASHRAE’s IAQ Procedure, we can proactively control formaldehyde and other harmful gasses and save energy by reducing our reliance on energy intensive “dilution ventilation” methods to maintain IAQ.

¹_{It is also worth noting that the “Maximum CO2 above Ambient” values in the revised Table 6-1 published in Addendum ab to 62.1-2022 result in CO2 limits, for the purposes of implementing CO2 DCV only, ranging from 1,000-2,500 ppm, depending on the space type.}

enVerid’s Sorbent Ventilation Technology (SVT) may be used to filter all the compounds included in Table 6-5 as well as CO₂. Click here to view efficiencies for SVT, and contact enVerid for help with ventilation calculations using the IAQ Procedure for your next HVAC project.