Review on Guardian AC4825 Filter B Replacement with Carbon Pre-Filters - 2 Pack FLT4825 + 10 Pack - Compatible with AC4300BPTCA, AC4900CA, AC4825DLX, AC4850PT, CDAP4500BCA, CDAP4500WCA by Monica Nixon

I decided to try these replacement filters instead of buying the manufacturer's filter, but when I installed this the air purifier didn't recognize its presence until I did Piece of cardboard added down, which rests on a pin that tells the device that the filter is installed. When I did this the unit started working but it was still flashing a red light indicating you have a dirty filter that needs to be replaced. So not really a suitable replacement.