3 Easy Ways to Improve Indoor Air at Your Business


Protect your employees and customers from the spread of viruses like COVID and the flu. Airborne viruses spread more easily indoors. Take simple steps to improve the air in your business.

1. Open doors and windows if the weather is nice and outdoor air is good

  • Bring in fresh air and pull out old air that might contain viruses like COVID and the flu. This helps prevent viruses from spreading as easily.
  • Help pull air through the heating, ventilation, and air conditioning (HVAC) system.
  • Place a fan pointed out an open window to blow air out and pull new.
  • Screens are recommended and required in some places. Removal of window screens will not increase the intake of fresh air.
business with fan on window with air blowing to the outdoor

2. Make a Filter Fan in 10 minutes

A filter fan is portable and affordable. It is quick and easy to build on your own. All the materials needed cost about $50. You can purchase all the supplies at your local hardware or home improvement store. Watch the video or follow the steps below to learn how to build your own filter fan.


    Items: 1 Box fan and 1 filter with a “MERV-rating” of at least 13

    Tools: Fitted clasps, duct tape, packing tape, or short bungee cords

    1. Attach the filter to the back of the fan by placing tape along the sides or wrapping bungee cords across the front and around the back. Make sure the arrows on the filter are pointing towards the fan.
    2. Place the fan at least 12 inches away from the wall. 
    3. Make sure the fan faces the middle of the room, away from walls and big objects.
    4. Cover cords properly. Make sure they are not tripping hazards.


    1. Turn off the fan periodically to avoid overheating. 
    2. Close all windows and doors while fan is turned on. 
    3. Replace filter every 3 months or when it looks dirty.


    • The filter fan captures and removes polluted air. 
    • The fan sucks air through the filter by trapping particles, such as dust and COVID virus.
    • Cleaner air comes out the other side.
    • The amount of virus particles, bacteria, and dust decreases in your business.

    3. Make sure your HVAC system is working well and maintained

    • Check that the restroom and kitchen exhaust fans are functional and operating at full capacity.
    • Check to see that the filters are pointed in the right direction. Most air filters have an arrow printed on their side that indicates the direction of airflow. The arrow should point in the same direction as the airflow in your HVAC unit.
    • If you rent your location, check your lease agreement to see if the filter system maintenance is covered by the landlord or property manager. If it is, you can ask when they last had the HVAC system checked by a specialist. 
    • Check the filters to make sure they are clean and do not need to be replaced. Schedule a consultation with a HVAC specialist to determine the best way to increase the system’s air filtration. 
    business with fan on window with air blowing to the outdoor

    Safer indoor air is just as important as safe water

    Improve indoor air at your business to keep your employees and customers healthy. Breathing safer indoor air is just as important as drinking and cooking with safe water. Ventilation helps prevent viruses like COVID and the flu from spreading, especially during the holidays when more people are visiting your business. More viruses are also circulating at this time of the year when more people spend time indoors. 

    Restaurant or business that is poorly ventilated

    restaurant poorly ventilated with a lot of particles in the air

    Restaurant or business that is well ventilated

    restaurant well ventilated with less particles in the air

    Common Questions and Answers


      Yes. Ventilation can help reduce virus particles in the air and prevent COVID and other viruses from spreading. It also helps remove dust, pollen, and other bacteria from the air. 


      Think about where people spend the most time and where the fan will be most beneficial to your employees and customers. Consider the following when choosing a location for the filter fan: 

      • Place it in an area where you cannot open doors or windows 
      • Place it near power outlets and away from foot traffic
      • Find a space where you can keep the fan at least 12 inches away from the wall and other electronics
      • Make sure cords are covered properly, and not a tripping hazard


      Ventilation increases air flow to dilute the number of harmful particles in the air. It moves air into, out of, or within a room. It improves air circulation by bringing in fresh air from outside. 

      Filtration traps harmful particles on a filter and removes them from the air.


      You will need a filter with a “MERV-rating” of at least 13 to attach to your box fan. This filter captures small and large mold, smoke, and allergen pollutants in addition to bacteria and virus particles. It decreases pollutants and lowers the amount of COVID and other viruses circulating indoors. 


      All the items needed to build a filter fan can be found at your local hardware or home improvement store. They can also be purchased online. Make sure to purchase a filter with a “MERV-rating” of at least 13 to attach to your box fan. 


      List of certified air filters: CARB-Certified Air Cleaning Devices


      Thank you for looking for ways to improve the air where you work. You have a right to safer indoor air. Get started by asking your boss, 

      • What you can do to help make indoor air safer
      • How to decrease COVID and flu virus indoors
      • If the HVAC specialist has been by recently
      • If the HVAC is maintained well and working 
      • If the HVAC system is filtering out COVID
      • If there is a small budget to build a filter fan for about $50


      business with fan on window with air blowing to the outdoor

      Business Resources

      Office of Labor Standards Enforcement Advice Line: 1-866-870-7725 

      Free Advice Line for workers and businesses seeking information or assistance with labor standards compliance or workplace issues. Toll free. Advice Line is supported in English, Spanish, Vietnamese, Chinese, Tagalog, and Visayan.

      Cal/OSHA Consultation Toll Free Assistance Line: 1-800-963-9424 or email [email protected]

      For workplace safety and health questions or assistance. You may also contact the Cal/OSHA Consultation Service Area Office nearest your workplace.


      ©2024 County of Santa Clara. All rights reserved.