And there really are a lot of good aftermarket options. Some may even be superior to OEM parts. But when it comes to air filters, at least, research has shown that there is little or no improvement in performance from using aftermarket air filters. This is not an easy question to answer.
In fact, some are meant to outshine the OEM counterpart. For example, an aftermarket filter may have better filtering properties or methods. Sometimes OEM products come with a fairly standard level of performance, and if you're looking for superior performance, you can look for an aftermarket product. Or maybe you're trying to save a little and are looking for off-brand products to use instead of the branded item.
Ultimately, there are aftermarket products that include filters that are better than their OEM counterparts, others that are lower quality, and some that stack at the same level. In Auto (similar to medium; the air does not contain a particle counter to adjust to air conditions, but instead asks you to enter the approximate size of your room, after which the machine chooses a fan speed that Molekule deems appropriate), the air performed worse, reducing particles by 0.3 microns at only 18.0% (ambient) and 26.4% (clean). In Silent, it performed even worse, reducing 0.3 micron particles by 6.5% (ambient) and 7.2% (clean). And in Dark plus Auto, with its primary PECO purification system turned off and its fan at the equivalent of a medium setting, it reduced them by 21.3% (ambient) and 18.0% (clean).
Interestingly, those numbers closely reflect our results in automatic configuration with the PECO system activated, suggesting the possibility that the Molekule Air depends mainly on its physical prefilter, not its patented PECO mechanism, to remove particles. There's no way to know without trying it. If you get the brand-name one, you can be reasonably sure that somewhere, people (like me) are testing exhaust air with expensive particle meters and will say they don't meet HEPA standards. Purifiers work best in an adjoining space; if you want to clean the air in both the living room and bedroom, for example, it's best to buy a purifier for each room or move a single purifier with you.
If the air quality is poor and you don't have an air purifier, an HVAC filter attached to a box fan is better than nothing. But those are rare circumstances, and the decision to pay more for a better filter or not depends mainly on whether cleaner air is a priority for you. In actual use, with the air in your home constantly recirculating through the ducts and passing through the filters each time, the cumulative effect of the filters increases. HEPA oven filters are usually a little cheaper than air purifying hepa filters, and will have a much larger capacity.
One possible reason the air performed worse than background reduction is that your fan agitated the air and prevented particles from settling. We think manufacturers' concerns are a little cautious, partly because a recent innovation in air filters allows for high MERV ratings (11 to 1) with low pressure drop. This prevents air from bypassing the filter around the edges and ensures that virtually all of the air drawn through the machine leaks HEPA, a design that is likely to contribute to the Mighty's excellent performance. In addition, an oft-cited comprehensive independent test of the effects of MERV filters 8 to 13 on HVAC airflow and energy consumption (an indicator of how hard the equipment is working) concluded that even “if no adjustments are made for the increased pressure drop of high MERV filters, airflow and energy penalties are unlikely to be severe at least, not until the filter is loaded with dirt.
Another rating method is the Clean Air Delivery Rate (CADR), a scale recognized by the Federal Trade Commission and Environmental Protection Agency that also measures air purifier efficiency. The HEPA filter is also treated with an antibacterial coating that, according to Aeris, “reduces the risks of infection by replacing filters. That's not just a financial concern, since air purifiers work best when cleaning a single room, it's worth considering separate machines for, say, the bedroom and living room. Start by determining the specific needs of the occupants of your home, which should be directly correlated with the CADR or MERV ratings of your air filters.