Indoor Air Quality During Smoky Conditions

The UC Berkeley campus has hundreds of buildings and each building performs differently based on its design, age, equipment, and critical human factors. 

"It Smells Smoky in Here..."

We can't stress enough the importance of keeping doors and windows closed when it's smoky outdoors. Indoor air will commonly smell of smoke during a wildfire event, but when we test it, we find it’s consistently better (i.e., containing lower particulate matter) than being outdoors. Most buildings contain MERV-rated filters that reduce harmful particulate pollution, but do not have charcoal filters that eliminate odors.

Facilities Services’ Role During a Smoke Event

Facilities Services is responsible for maintaining critical air-conditioning and ventilation systems throughout the year. Their teams are incredibly busy on hot and smoky days monitoring HVAC performance. Air filters are replaced on a schedule throughout the year, but Facilities Services will monitor filters during and after a prolonged smoke event and change as neededLearn more about ventilation in buildings on the Facilities Services website

Employees with indoor air quality concerns can:

  • Request an indoor air quality survey from EH&S:

    • Call (510) 642-3073 or email

    • Please note, staff are incredibly busy on smoky days so response times may be impacted. EH&S has also installed indoor PM2.5 sensors in various campus buildings to evaluate indoor air quality; data from these sensors is monitored during wildfire smoke events to assist with campus decision-making. Learn more about air monitoring.

  • Based on operational needs, employees can work with their supervisor to request alternate working arrangements. The Campus AQI Decision-Making Matrix describes actions based on outdoor conditions during wildfire smoke events. 

Laboratory Buildings

The HVAC systems serving laboratory spaces are different from those serving other types of spaces on campus.  The system serving a lab space supplies 100% outside air, meaning no air exhausted from a lab space is recirculated back into the system - it is all exhausted outside the building. 

Indoor Air Quality in Labs

Non-Laboratory Buildings

HVAC systems serving other types of spaces, such as office, classroom, and/or community spaces have different ventilation requirements than laboratory buildings. Systems serving non-laboratory spaces are designed to bring in at minimum the amount of outside air required for the design occupancy of the spaces (or the measured occupancy in the case of Demand Controlled Ventilation) and mix it with air returned from the spaces. Most systems are also designed to bring in more outside air (up to 100%) when outdoor conditions are favorable (i.e., not too hot or cold). This mixed air is then filtered at the central unit before it is supplied back to the space.

Indoor Air Quality in Classrooms and Offices

Buildings without Mechanical Ventilation Filtration Systems

A subset of campus buildings and many housing facilities do not have mechanical ventilation filtration systems (see UHS list). There are a number of ways to reduce smoke exposure in buildings or homes without ventilation & filtration:

  • Smoke can irritate the eyes and airways, causing cough, a dry scratchy throat, runny nose, trouble breathing, and irritated sinuses. Stay hydrated by drinking water during heavy smoke events.
  • Stay inside with the doors and windows closed.
  • Review information on when to use a portable HEPA filter unit from Facilities Services.
  • At home, create a “clean room” with a portable HEPA air purifier properly sized for your space. Do not add to indoor air pollution. Do not burn candles or use gas, propane, woodburning stoves, fireplaces, aerosol spray, fry or broil meat, smoke tobacco products, or vacuum. All of these can increase air pollution indoors.
  • Do not add to indoor air pollution. Do not burn candles or use gas, propane, woodburning stoves, fireplaces, aerosol spray, fry or broil meat, smoke tobacco products, or vacuum. All of these can increase air pollution indoors.
  • Long-term smoke events usually have periods when the air is better. When air quality improves, even temporarily, air out your space to reduce indoor air pollution, and step outside yourself when you have a chance.
  • Seek shelter elsewhere if it is too warm to stay inside with the windows closed. A list of designated “cleaner air shelters” is posted on the UHS website.
  • Outdoor workers and employees in campus buildings without mechanical ventilation filtration systems should review EHS 704 Wildfire Smoke Protection & N95 Respirator Training and may pick up N95 respirators from EH&S when the air quality index is unhealthy outdoors (>150). A N95 distribution schedule will be posted on the EH&S Wildfire Smoke web page when needed, or you may email