DO AIR PURIFIERS WORK WITH THE WINDOWS OPEN?

Air Purifiers work by circulating the air in a room and filtering contaminants such as pet dander, allergens, microbes, airborne pathogens, VOCs and much more from the air to create a healthy indoor environment. People often ask the practical question, “Do air purifiers work when windows or doors are open?” so we’ve decided to capture a detailed response in this article. Some people may wish to keep their windows open for a specific reason – such as, reducing VOCs & Formaldeyde or to simply make the room less stuffy or hot, but now let’s find out whether keeping that window open will stop the air purifier from working.

AIR PURIFIERS AND OPEN WINDOWS CAN ACTUALLY BE A VERY EFFECTIVE INFECTION PREVENTION CONTROL METHOD.

Extensive Research and Studies have shown that by opening windows you increase the air flow and ventilation into a room, significantly lowering the CO2 and thereby the risk of contamination with a virus when there is poor air flow. Having an in-room air purifier helps additionally by constantly filtering out any remaining airborne pathogens that may be in the air. Our reccomendation when it comes to ventilation in a space, is that you always need to ensure you are cleaning the air as well as introducing more air into it.

AIR PURIFIERS ARE MORE EFFECTIVE AT REDUCING PARTICULATE MATTER WHEN WINDOWS ARE CLOSED.

However, air purifiers are definitely more effective when windows are closed due to the fact that they’re designed to cope with a set volume of air and if you increase that volume by opening the window, the purifier will be less efficient at reducing particulate matter counts.  When you open windows, you can potentially add pressure to the air purification process as the air inside quickly becomes subject to whatever particulate matter are present outdoors, so you’re massively expanding the volume of air that has to be dealt with especially if the outside air is highly polluted.

To cite an example:  Think about how a refrigerator works. It’s primary task is to cool the air inside of it based on it’s capacity.  If you leave the door of the refrigerator open, the contents will still be cooled to an extent, but you’ll be reducing the performance of the fridge significantly because you’re introducing a lot more air to the cooling units than they are designed for. An air purifier operates on a similar principle in terms of the fan and filters volume capacity per hour.

SO IS IT BEST TO KEEP MY WINDOW CLOSED WHEN THE PURIFIER IS ON THEN?

No, that’s not the requirement at all. You need to consider a few key factors:

#1 How clean is the air outside?

• Is it dirty, smoggy, polluted? Is anyone having a bonfire nearby? Are you on a busy road or near an industrial area? If this is the case, you’re probably going to be best keeping that window shut.  If you’re in a low pollution area, then an air purifier is going to work fine, alongside the fresh air being introduced.

#2 How long do you plan to have the window open?

• If you’re in a medium polluted area – Time is the determining factor for whether or not an open window will or will not reduce the indoor air quality in your building. The longer the window is open, the more work you are expecting the air purifier to perform.

#3 How many windows do I plan to open?

• Airflow with 1 vs 2 or more windows open can be dramatically different. With 2 or more windows open, often the air purifier will have reduced effectiveness on cleaning the air you breathe. With only 1 window open, there is some external air entering the room but the purifier can at least work with some efficiency. This is because the amount of disturbance in the room’s air flow is typically much smaller.

INTERESTING DATA (courtesy of smartairfilters.com)

One organisation in Beijing ran 6 tests in a standard hotel room to measure the difference in air quality when the windows were opened vs closed. With the window closed, the air purifier reduced particulate matter by an average of 90% after 20 minutes (blue lines). With the window open, the air purifier managed a 60%  reduction (Red Lines).

The data shows that from an air pollution point of view (particulate matter) the air purifier works best when the window is shut, but the interesting part is that even with the windows open, it is still possible to dramatically reduce indoor particulate matter.

FINAL THOUGHTS

It’s perfectly acceptable to open your windows and operate an air purifier if:

• Your outdoor environment is relatively clean and low pollution levels reported
• Your room is newly painted or fumed and you want to clear the odours fast.
• There are immediate indoor air quality problems (High CO2 for example)
• You have little or no mechanical ventilation

It’s advisable not to open your windows and operate an air purifier if:

• Your outdoor environment is heavily polluted
• You have bad air quality issues indoors and the purifier needs time to properly clean it.

Wondering which air purifier might be the best one for you?

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