Product review (4 stars): Excellent for Evaporation Humidifiers
I purchased this filter for my Graco home humidifier.  I regularly performed operational maintenance on my humidifier, including washing the filter.  Despite the maintenance the filter slowly became discolored from the natural pollutants and minerals contained in my water.  This Graco Filter helped solve my problem.

I carefully care for the filter.  To avoid frequently replacing the filter,  I use a procedure that can extend the life of the filter.  When the filter forms a crust, I soak it for awhile in vinegar water (usually 1 part vinegar to 4 parts water).  After soaking I carefully rinse the filter several times in fresh water.

The Graco humidifier that I use is an evaporation style machine.  To work properly, the "filter" must be free of pollutants, as the machine adds moisture to the air by having a fan blow air through the sponge type filter (exactly like the "swamp coolers" so popular in arid climates).  Clogs decrease effectiveness and add pollutants to the air in the room being used.  Accordingly, in addition to carefully maintaining the filter, I add  KAZ Humidifier Bacteriostatic Treatment to the reservoir to prevent the growth of bacterial agents. (<a data-hook="product-link-linked" class="a-link-normal" href="/KAZ-Humidifier-Bacteriostatic-Treatment/dp/B0009GZLYU/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">KAZ Humidifier Bacteriostatic Treatment</a>

When properly maintained, the Graco Humidifier Replacement filter is an excellent product.  I recommend this filter for evaporation humidifiers.