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Does adding a carbon layer reduce particulate effectiveness?

I recently published tests showing that carbon actually removes VOCs. But adding that carbon layer raises a question: adding carbon means the fan has to power through yet another layer of resistance. Does that make purifier less effective at removing particulates?

Methods

To test this question, I ran 10 room tests with the Cannon and 10 tests with the Original DIY in the same 15m2 Beijing apartment as my earlier tests without a carbon layer.

I measured how much particulate it removed with a Dylos particle counter and compared the particle counts (1) before I turned on the purifier at night and (2) the average of the last four hours before I woke up in the morning.

Results

With the additional carbon, the Cannon particulate effectiveness dropped 1-2%. Thus carbon has a very minor negative effect on the Cannon.

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However, the Original DIY had a harder time powering through the extra layer. Its 0.5 micron effectiveness dropped 19%, and 2.5 micron effectiveness dropped 15%.

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Conclusion

For people who need carbon (and that is not everyone), I would recommend adding the carbon to the Cannon, but I would think twice about adding carbon to the Original.

As always, I’m posting the raw data and more details on the test for fellow nerds below.

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