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Community and Q&A

Spare the Air days and mechanical ventilation: are filters or cutoffs recommended?

Bill Fitler | Posted in Mechanicals on

Our local air pollution control district is promoting awareness of days when air pollution is particularly onerous (in our area due to winter still air and wood burning fires). Has anyone analyzed the need for HRV air filters or temporarily turning off mechanical ventilators in these conditions?

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  1. Stephen Sheehy | | #1

    I replaced my HRV filters with MERV 13 filters. I assume all HRVs have filters. Mine (Zehnder) came with MERV 8, I think.
    I don't know that filters will stop smoke particulates, though. Supposedly, a MERV 13 will remove "most smoke," whatever that means.

  2. GBA Editor
    Martin Holladay | | #2

    I don't advise you to turn off your HRV on these "bad air" days, but Stephen is right: a filter with a MERV rating will filter particulates (although there will always be some particulates that common filters can't handle).

    The higher the MERV number, the smaller the particles that it can filter. There is a downside to a MERV filter with a high number: it raises the static pressure of your ventilation system, increasing the load on your fan motors (and therefore increasing your energy bills). Check with the HRV manufacturer to determine what type of MERV filter will work with your particular HRV.

  3. Aaron Gatzke | | #3

    The MERV 13 filters will remove some of the particulates but only activated carbon/ charcoal will remove all the wood smoke. However, it is a much more expensive filtration system than just a pleated filter as they are generally added to the fresh air supply leaving the HRV. They also have a built-in fan reduce the back pressure of the filter. Lennox makes one such model. I cannot attest to how effective it is or how much it costs to run. If no one has sensitivities in your home, you may be fine with the MERV 13 filter. There are also,stand alone air purifiers if necessary. IQ Air makes a good model. Not cheap but effective.

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