Ozone
About This Health Driver
Ozone (O3) in indoor environments comes from two sources: outdoor tropospheric ozone that infiltrates through the building envelope, and indoor-generated ozone from some air purifiers, photocopiers, laser printers, and electrical equipment. Outdoor ozone levels peak during hot, sunny afternoons in areas with vehicular traffic and industrial emissions.
How It Affects Bodies
Ozone is a powerful oxidant that damages respiratory epithelium, triggers inflammatory cascades, and produces reactive oxygen species. Chronic exposure is associated with systemic oxidative stress and immune activation. Ozone reacts with indoor surfaces and chemicals to produce secondary pollutants including formaldehyde, ultrafine particles, and organic radicals, amplifying its impact beyond direct inhalation effects.
Where It Comes From
- Outdoor infiltration - tropospheric ozone entering through the building envelope, particularly in high-smog regions
- Ozone-generating air purifiers - ionizing air cleaners and ozone generators marketed for air purification
- Laser printers and photocopiers - ozone production during operation
- Certain electrical equipment - motors and transformers producing trace ozone
How to Address It
- Activated carbon air handling filtration - removes ozone from incoming ventilation airMechanical
- CARB-certified air purifiers only - no ozone-generating devicesOperations
- Sealed-mode operation protocol - close windows and recirculate filtered air during high-ozone eventsOperations
- Ventilated printer areas - exhaust ventilation for home office printer/copier zonesMechanical