Tips for using a portable HEPA filter

Portable HEPA filter, connected to a battery for a longer charge. Photo by: C.Suthorn / cc-by-sa-4.0 /

After I shared my travel experience last week, a couple of readers reached out asking for more details on using a portable HEPA filter, essentially a small air filter that can be moved from one place to another.

Scientific research has shown that air filters can be valuable tools for reducing the risk of COVID-19, along with other respiratory viruses and pollution concerns, such as wildfire smoke. These filters essentially remove dangerous particles from the air, making indoor spaces safer.

These air filters can be costly (prices range from $50 to $1,000), but may prove to be a helpful long-term investment if used often. My partner and I used ours while traveling, as well as in our apartment when we have guests over and during periods of intense wildfire smoke pollution in New York City.

Here are a few tips and resources about using HEPA filters:

  • This spreadsheet, compiled by the air quality recommendations site Clean Air Stars, lists hundreds of portable air filters. For each filter, the spreadsheet includes information about their performance, cost, whether you need to purchase filters separately, and other details.
  • Clean Air Stars also offers a recommendation tool that will suggest how many air cleaner models and at what fan speed might be needed for a room of a given size.
  • This is the portable filter that I use: the QT3 Portable Air Purifier from Smart Air. It’s fairly small and lightweight, and filters 40 cubic meters per hour.
  • You might see filter options boasting their clean air delivery rate, or CADR. This is a measurement of an air purifier’s effectiveness, telling you how much filtered air the machine can provide in a given timespan (cubic meters per hour, cubic feet per minute, etc). For more details, see this blog post from Air Conditioner Lab.
  • Understanding your air filter’s CADR is important because it tells you the range in which your device works. For example, a smaller filter with a lower rating might clean the space immediately in front of you on a train, but would not clean the entire car. Smaller filters might also need to run for a longer time to clean an enclosed space (such as a hotel room).
  • If you’re traveling with an air filter, a portable battery can be helpful to extend the device’s runtime. My filter runs for a couple of hours on its own battery power, but will last for much longer if plugged into a portable battery.
  • Research and recommendations from air filter providers recommend placing your filter close to you and facing you, to get the clean air delivered as close to you as possible. 
  • If you’re also using a CO2 monitor, it’s important to note that the monitor’s reading likely won’t change due to a HEPA filter. CO2 monitors measure clean outdoor air in a space, so they do not register when existing air is filtered. A monitor that measures particle pollution would be needed to see the difference your filter is making.
  • Know when to change your device’s air filter! Many devices have built-in indicators telling you to do this (i.e. a light that flicks on when the filter needs replacement), while others will come with instructions recommending a filter change after a given period of time.
  • Air filter use is not an exact science. While you can find answers to some questions in scientific literature, others might require crowdsourcing on social media or trial and error on your own to find what works best for you. Overall, though, remember that any use of an air filter will be better than taking no steps to clean your air.

I hope this is helpful. If you have more questions (or would like to share your own recommendations), please reach out!

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