Is penny-wise pound-foolish with replacement filters?

October 30, 2008 4:15 PM

With some products, the off-brand is as good as any other brand, sometimes even coming off the same production lines in the same factories. With other products, there is a quality difference between brands. How about for replacement HEPA filters for a Kenmore air cleaner? (And, as a bonus, should I believe the warning against washing and reusing the charcoal pre-filters?)

My Kenmore air filter has charcoal prefilters to replace every three months, and a HEPA filter to replace yearly. The Kenmore replacement HEPA filter is $110, while this aftermarket one, for example, is $68 including shipping. Both claim to capture 99.97% of particles down to .3 microns. I picked my air filter carefully based on reading about tested differences in performance, so I don't want to cheap out now if there's a quality difference, but I don't want to pay extra if there's not.

For the bonus question, the charcoal pre-filters come with the warning, "DO NOT try to wash and reuse either the HEPA filter or the pre-filter," but when I take out the pre-filters, they sure look like a good hosing off and a thorough drying in the sun might make them perfectly serviceable again. Would performance be degraded?

posted by daisyace to shopping (4 comments total)

Charcoal...like activated charcoal? Washing isn't going to rejuvenate an activated charcoal filter. That's what's inside most water filters.
posted by madmethods at 4:20 PM on October 30, 2008

All that nasty überfine dust is going to stay in there, stuck to the particles and making the filter stuffed up.
posted by dunkadunc at 4:34 PM on October 30, 2008

HEPA filters (coming from a biologically clean room perspective, where I have some experience) have equivalent filtering efficiency, otherwise they can not be called HEPA. Beware of "HEPA type", "HEPA like", "97.7% HEPA", etc....

What does change depending on the brand is the durability, both in terms of the time it takes for them to saturate and how resistant they are to wear and tear.

Activated charcoal is not used to capture dust in the way a sand sieve captures pebbles. It uses Van der Waals force and sometimes chemical reactions to capture particles. It works at the atom or molecule level. Sometimes it is treated with other chemicals to absorb specific contaminants. Washing with water will remove some of the larger particles that have become mechanically trapped in the filter, but will not "reactivate" the charcoal.

Charcoal is reactivated or regenerated in very high temperature ovens, in the absence of oxygen or other reactive gases. Not a home project usually.
posted by dirty lies at 4:56 PM on October 30, 2008

Keeping with the penny-wise theme, if you have been using your air filter in normal household conditions, it will likely be still activated at the time the manufacturer recommends replacement.

You can take the charcoal out of the filter, put it in a shallow bowl, and use it to deodorize the fridge, a closet, whatever.
posted by dirty lies at 5:00 PM on October 30, 2008