Can You Run an Air Purifier With the Window Open?

The short answer is yes, you can run an air purifier with the window open. However, doing so may impact the effectiveness of the air purifier. In this article, we’ll explore the reasons why you may want to run an air purifier with the window open, factors that can reduce the air purifier’s performance, and tips to maximize its effectiveness if you need to have the window open.

Why Run an Air Purifier Near an Open Window?

There are a few reasons why you may need or want to run an air purifier near an open window:

• To remove odors, smoke, pollen, or other pollutants entering through the open window.
• To increase airflow and ventilation.
• If placing the air purifier elsewhere would block walkways or furniture.
• If noise from the air purifier is less bothersome near the open window.

For example, you may want to open a window to let in fresh air but also need to run an air purifier to filter out pollen, dander, or other allergens coming in from outside. An open window near a busy road could also allow pollutants like car exhaust to enter, which an air purifier could help remove.

Factors That May Reduce Air Purifier Effectiveness

While running an air purifier near an open window is possible, there are some factors that may reduce its effectiveness:

• Air exchange rate – Open windows increase ventilation and airflow through a room. This quick turnover of air from outside can limit the time the air purifier has to filter and clean the air.
• Unpurified air entering – With a constant source of unfiltered air coming in through the window, the air purifier has to work harder to keep up.
• Allergens and pollutants – Depending on wind and weather conditions outside, running the air purifier near the open window may draw in more of the particles you’re trying to avoid rather than push them out.
• Room size – Air purifiers are usually designed for closed rooms of certain sizes. Opening a window can throw off that balance and reduce the unit’s cleaning capacity for the space.

The rate of air exchange from outside, combined with the unit’s CADR (clean air delivery rate) will determine if the air purifier can still effectively clean the air with the window open. Larger capacity air purifiers will be better equipped to handle open windows in small spaces.

Tips for Running an Air Purifier Effectively Near an Open Window

If you need to run an air purifier with the window open, the following tips can help maximize its performance:

• Close all other windows and doors – This contains the area the air purifier needs to clean.
• Position the air purifier 2-4 feet from the open window – Lets it focus on filtering the incoming air.
• Point the air purifier towards the window – Helps direct any allergens and pollutants back outside.
• Reduce window opening size – Start with windows cracked open just a few inches to allow some air exchange while minimizing impact on the air purifier.
• Use highest fan setting – Runs the air purifier at maximum filtration capacity.
• Supplement with box or tower fans – Strategically placed fans can help direct incoming air towards the purifier and disturb stagnant pockets of air.
• Close the window periodically – Gives the air purifier time to properly clean the room’s air without constant dilution.

Monitoring pollen counts and air quality reports can help determine when it’s best to shut the window altogether. At night or during periods of poor outdoor air quality, you may want to keep windows closed and rely solely on the air purifier.

When an Air Purifier May Not be Enough

While air purifiers can help clean the air, they have limits. If you are experiencing very poor outdoor air quality or are highly sensitive to pollens or pollutants:

• Sealing off the room completely and running the air purifier may be a better approach.
• Using HEPA air filters in HVAC systems can provide whole-home air purification.
• Portable air conditioners with HEPA filters offer an alternative to open windows for warm rooms.
• Consulting an indoor air quality expert can help identify the best solutions for your situation.

Air purifiers work optimally when windows are kept closed, but can still provide some benefit if the factors reducing their effectiveness are minimized. Try the tips suggested here if you need to have a window open near your air purifier.

Frequently Asked Questions

1. Do air purifiers work with windows open?

Air purifiers can still provide some benefit with windows open, but their effectiveness will be reduced. The constant influx of unfiltered air limits the time the purifier has to clean the room’s air. Strategic purifier placement and fan usage can help maximize air cleaning.

2. Should you keep windows open with air purifier?

It’s generally recommended to keep windows closed when running an air purifier, especially if trying to control a specific indoor air pollutant like pollen. Open windows increase ventilation but allow more allergens and pollutants to enter unchecked. However, you may need to open windows periodically for fresh air.

3. Do air purifiers work better with windows closed?

Yes, air purifiers work significantly better with all windows and doors closed. This contains the area the purifier needs to clean and prevents constant dilution with untreated outside air. Closed rooms allow air purifiers to recirculate and filter the room’s air multiple times.

4. Should you run air purifier all the time?

Many experts recommend running air purifiers continuously if you want to maintain improved indoor air quality. Airborne particulates accumulate quickly after an air purifier is turned off. However, some models have an auto mode that monitors air quality and adjusts operation as needed to save energy.

5. Is it a waste to run air purifier with window open?

It’s not a complete waste, as the air purifier can still filter some of the incoming air. However, the benefits are significantly reduced compared to running with windows closed. It’s best to limit window opening size, point the purifier towards incoming air, and maximize fan speeds.

6. Do air purifiers pull air from outside?

Air purifiers are designed to filter and recirculate the air within a closed room. They don’t actively pull air in from outside sources. However, opening windows and doors near an air purifier can impact the air currents in a way that draws outdoor air into the room and purifier intake.

7. Can air purifiers remove car exhaust from outside air?

Air purifiers with activated carbon filters can help remove some vehicle exhaust that enters indoors from open windows or doors. However, very high levels from direct sources like highways may overwhelm an air purifier. Sealing off rooms or using whole-home air purification is more effective.

The Bottom Line

Running an air purifier near an open window is generally not ideal, since the constant influx of outside air reduces the unit’s cleaning capacity. But strategic placement and fan usage can still allow it to filter out some allergens, odors, and pollutants entering indoors. Just don’t expect the same level of air purification compared to running with all windows firmly shut.

For further reading, check out this article from EPA.gov on the use of air purifiers and filters in the home.