[ryanmarsh]

The contrast indicates that regularly replacing the HEPA filters of APs could represent an effective method of avoiding increased endotoxins in the filtered air.

That's a pretty clickbaity paper title. The lede was buried. A better title would have been: Regularly replacing HEPA filters may reduce endotoxins in filtered air

I'm a high school drop out so what do I know.

[bricemo]

It’s not that simple though, the study states that replacing the filters removes large endotoxins, but not small ones. The small ones are still present

[Havoc]

>The small ones are still present

Bit strange given that you've removed the alleged source of the problem (stuff caught in old filter).

[enragedcacti]

From my understanding the filtration process itself (through a dirty filter) is creating the endotoxins that wouldn't have otherwise been present (although other pm2.5 particles would be of course).

e.g. A car with a catalytic converter avoids increases of certain gases in the air, but it doesn't reduce what is already present.

In that light both the title and the suggested mitigation seem pretty straightforward.

[kkfx]

The point is probably about concentration: if certain "pathogens" (no matter their nature, it's valid from all bacteria, viruses, poisonous chemicals etc) are present but below a certain concentration they are effectively harmless. If more concentrated they might be harmful. Under certain condition a local concentration might form a colony that act as a persistent source of potentially harmful "pathogens". A bit more complex, but a good generic description.

What it's not clear to me is the definition of "purifier" and they operating principle: VMCs are normally harmless because they do not blow humid air and they keep air flowing so it's hard to offer room for "colonization" in most cases. That's the same principle we have for modern water heaters, classic ones, large pressurized balloons filled of hot sanitary water do require a regular daily extra-heat-up against legionella, modern ones with a not pressurized hot-water balloons and just a spiral pipe inside to "instantaneously" heat the sanitary water flowing in the pipe in most country do not demand anti-legionella heating cycle because they do not offer room for it's development. So much of the point of this study should be define the kind/family of devices they have testes.

[bombcar]

"Dirty filters can release bacteria poop" wouldn't get as much interest.

[qorrect]

"Your house is full of invisible poop" would definitely get my attention

[outworlder]

"Overall, endotoxins deposition in the alveolar region increased regardless of whether the air purifier was loaded with used or new HEPA filters."

[CamperBob2]

Translation: "This sounds bogus. Wait for replication."