California Air Resources Board

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  • Presentations (PDF)

Updating the Indoor Air Quality Guidelines for Nitrogen Dioxide

November 19, 2025 at 4 p.m. PT

The California Air Resources Board (CARB) invites you to participate in our third public workshop discussing potential updates to the California indoor air quality guidelines for NO₂.

1. At the first workshop, international and state health agencies, health experts, and community-based organizations presented information on the importance and need for up-to-date indoor guidelines as well as recent approaches and potential challenges to updating the guidelines.
2. The second workshop covered CARB’s potential approaches based upon the information presented in the previous workshop.
3. This third workshop will cover CARB’s proposed guideline values and the rationale for the approach chosen.   

Public Workshop #3

Date: Wednesday, November 19, 2025
Time:  4 p.m. to 6 p.m. PT
Location: Zoom Webinar
GovDelivery Bulletin Announcement

To attend the workshop, please register.
After registering, you will receive a confirmation email with information about how to join the webinar by computer or by telephone. Note:

• The agenda will be posted ahead of the meeting. 
• Comments may be submitted here.     

Purpose of Workshop

CARB is evaluating the health evidence and approaches for updating California's indoor air quality guidelines for NO₂ to protect public health. 

CARB hosted two previous workshops (May 16, 2023 and May 30, 2024) in which international and state health agencies, health experts, and community-based organizations presented information on the importance and need for up-to-date indoor guidelines, approaches to consider, and potential challenges.  

CARB evaluated several approaches for updating California's indoor air quality guidelines for NO₂. Based on information gathered at the two workshops, and previous work by other guideline developing health agencies, CARB has identified an approach that is scientifically sound, and that has guideline values that best protect public health, particularly for sensitive receptors. In this third workshop CARB will present the approach selected and the proposed 1-hour and 24-hour values. After the presentation, CARB will open the meeting for comment and discussion. Our objective is to get feedback on the proposed guideline values, and especially how these new values can be messaged and best leveraged by those in underserved communities. 

Background

CARB’s existing 2005 indoor air quality guidelines for NO₂ and other pollutants were developed as part of the 2005 Indoor Air Quality Report to the Legislature. They were based upon CARB’s outdoor standard for a 1-hour averaging time, and WHO’s indoor guideline for a 24-hour averaging time. These guidelines were one of the first efforts to provide information on safe levels for air pollutants indoors. Since the 2005 report, numerous studies have been published about the health effects of NO₂. Other agencies, most notably Health Canada and WHO, have continued to update their indoor guidelines and adopt lower indoor pollutant levels to protect public health. The most recent Health Canada and WHO guidelines for indoor NO₂ levels are significantly lower than CARB’s current NO2 guideline levels and support the need to reevaluate CARB’s indoor air guidelines.

Contact

If you have questions regarding this workshop, please contact Jeffery Williams in CARB’s Research Division at Jeffery.williams@arb.ca.gov.   

If you require a special accommodation or need this document in an alternate format (i.e., Braille, large print) or another language, please email Jeff Williams as soon as possible, but no later than ten business days before the workshop. TTY/TDD/Speech to Speech users may dial 711 for the California Relay Service.

Workshop Presentations & Transcripts

A recording of the workshop will be made available here after the workshop.

• Presentations (PDF)