A230 / A231

Avoid Tailulu, it's a garbage rebadged brand. Winix 5500-2 for the living room. Winix A230 for your bedroom. Keep in mind: Clean Air Delivery Rates (CADRs) apply to the highest airflow speed/setting only. Lower settings have lower CADRs. In all likelihood, disabling PlasmaWave (the ionizer) will decrease Pollen CADR. The Built Environment Research Group showed the Winix 5500-2 showed an 18% decrease in Pollen CADR during their testing: [https://www.built-envi.com/wp-content/uploads/IIT-CADR-Testing-WINIX-5500-2-October-2021.pdf](https://www.built-envi.com/wp-content/uploads/IIT-CADR-Testing-WINIX-5500-2-October-2021.pdf) Another note: the Winix 5500-2 is being phased out. But... filters will be available in the years to come. That would be [Filter H – 116130](https://www.winixamerica.com/product/filter-h-116130/). The genuine Winix filter is cheaper on Amazon.

Freestanding air purifiers can't overcome walls and doors. You need one for each room or area. **Therefore we need each room's length x width x height to calculate Clean Air Delivery Rates (CADRs).** As for your questions: 1. Winix is good, but not the best. I'd generally say Coway is the best in terms of quality for consumer-grade units. 2. PlasmaWave is Winix's name for their bipolar ion generator. It can be turned on or off. PlasmaWave (in practice) seems to enhance Pollen CADR. I believe Levoit's PlasmaPro is also generates positive and negative ions. 3. HEPA vs. "True" HEPA is mostly marketing. What *is* important is listing the appropriate standard, the filter class (where applicable, like H13 or H14), and the filtration efficiency % at a particular particle size or sizes. 4. DIY Corsi-Rosenthal boxes can work very well, which typically use MERV 13 furnace filters. MERV 13 is a lower filtration efficiency than HEPA, meaning it captures fewer particles of certain sizes on a single pass. But... since MERV 13 is less restrictive, it can achieve more passes through the filter media faster which can result in higher CADRs. (Assuming sufficient airflow.) If you wanted to build a C-R box, I would recommend doing so with PC fans. Drawback: most C-R box configurations do not specify fine mesh pre-filters. Without these, the MERV filter media can clog sooner with coarse particulates such as visible dust and hair. 5. "Level of filter": I assume you mean filtration efficiency of a mechanical filter. Mold, fungus, pollen, and viruses are bioaerosols. They can be captured with HEPA, EPA, or certain MERV filters (generally MERV 13 and higher). EPA and MERV 13 filters are a lower filtration efficiency than HEPA, so it will allow more particles through on a single pass. But EPA and MERV 13 can achieve more filter passes and higher CADRs than HEPA with proper airflow for less money. 6. As for secondhand purifiers, that's up to you. Sometimes you can find items that are barely used. But it's also possible purifiers were used in highly polluted environments (e.g., lots of mold or post-fire remediation) or could have bed bugs inside. 7. The blue box looks like an air scrubber. These are meant for more challenging and large environments, e.g. during renovation, fire remediation, or serious mold remediation. Air scrubbers tend to be quite loud.