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What I am wondering about: I worked with and designed clean room equipment in the nineties. I remember that HEPA requires a considerable pressure difference whi
by chopin 6y ago
What I am wondering about: I worked with and designed clean room equipment in the nineties. I remember that HEPA requires a considerable pressure difference which cannot be delivered by an axial fan. You'd need a radial one which can deliver a considerable differential pressure, at cost of throughput (where the axial fan shine). If you strap a HEPA to an axial fan and seal it, the fan runs effectively "empty", i.e. it displaces only little air which most likely even doesn't pass the filter. That's why HEPA filters work in vacuum cleaners since they have radial fans. I am astounded by the results of the post.
I tested simply with a laser. In a normal room you can see the laser beam in dark. If you have a good purifier, you can't.
- Traubenfuchs 6y ago> In a normal room you can see the laser beam in dark. Dear god, do you live next to a coal plant? I would argue that in a normal room one should NOT be able to see the laser beam!
- joncrane 6y agoYou'd be surprised how "dirty" (dusty) the air inside houses is.
- metiscus 6y agoEspecially given the relatively wide range for age and consequently construction type. I've found that newer drywall construction tends to be more dusty in my limited experience than well maintained plaster and lath.
- yborg 6y agoWall-wall carpet, especially old carpet, is a dust factory.
- metiscus 6y agoMy house has tile floors which get visibly filthy really quickly. I have a roomba and I personally clean the floors quite often manually. In my parents house which had wall to wall carpet, they would vacuum relatively infrequently but the same amount of dirt was likely being tracked in and around. Their house was more dusty than mine seems to be because of the fact that carpet tends to hide how "dirty" it is.
- myself248 6y agoLatch the laser beam on, aim it across the room, and go thump your hand on the couch cushions a few times.
- rootusrootus 6y agoRed laser, sure, but in my experience green lasers are significantly brighter and it's much easier to see the beam in clear air (though if you're human you probably need to look down the beam to spot it, my cats can see the beam horizontally and they swat at it).
- yborg 6y ago>If you strap a HEPA to an axial fan and seal it, the fan runs effectively "empty", i.e. it displaces only little air which most likely even doesn't pass the filter This. I tried a 3M MERV 12 filter taped to the intake of a cheap $12 box fan and the airflow through the fan went to effectively zero. The fan actually was pulling more air from the front of the fan around the sides of the fanbox than through the filter. Increasing the fan speed just increased this backflow. You are spot on with a radial fan being what you want here, and I notice that basically every commercial air purifier uses such a fan.
- EricE 6y agoRadial fans are a lot quieter for the volume of air delivered too. Wish I could find a room humidifier with a radial fan but all I can find are axial fan designs :p